Sum of series $sumlimits_{k=0}^infty frac{a^{k^2}}{k!}$











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I am looking at this sum:



$displaystylesum_{k=0}^infty frac{a^{(k^2)}}{k!}$ for some $a>0$.










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    Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
    – Daniele Tampieri
    Dec 4 at 19:52















up vote
-3
down vote

favorite












I am looking at this sum:



$displaystylesum_{k=0}^infty frac{a^{(k^2)}}{k!}$ for some $a>0$.










share|cite|improve this question




















  • 4




    Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
    – Daniele Tampieri
    Dec 4 at 19:52













up vote
-3
down vote

favorite









up vote
-3
down vote

favorite











I am looking at this sum:



$displaystylesum_{k=0}^infty frac{a^{(k^2)}}{k!}$ for some $a>0$.










share|cite|improve this question















I am looking at this sum:



$displaystylesum_{k=0}^infty frac{a^{(k^2)}}{k!}$ for some $a>0$.







sequences-and-series power-series






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edited Dec 4 at 20:47









Did

245k23219453




245k23219453










asked Dec 4 at 19:49









E Onaran

62




62








  • 4




    Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
    – Daniele Tampieri
    Dec 4 at 19:52














  • 4




    Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
    – Daniele Tampieri
    Dec 4 at 19:52








4




4




Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
– Daniele Tampieri
Dec 4 at 19:52




Hi and welcome to the Math.SE. Why this problem is interesting for you? And what did you tried in order to solve it? I you want to get help from other members, you should try to add as more context as possible to your question, in order to help them help you.
– Daniele Tampieri
Dec 4 at 19:52










1 Answer
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If I get to choose $a$ I choose $1$ and the sum is $e$.



For $a gt 1$ the sum diverges.



For $0 lt a lt 1$ it will converge quickly but I suspect has no easy answer. Alpha says that for $a=frac 12$ the sum is about $0.531576$ but does not give a closed form.






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  • This is a special function, theta or something.
    – Did
    Dec 4 at 23:57











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
1
down vote



accepted










If I get to choose $a$ I choose $1$ and the sum is $e$.



For $a gt 1$ the sum diverges.



For $0 lt a lt 1$ it will converge quickly but I suspect has no easy answer. Alpha says that for $a=frac 12$ the sum is about $0.531576$ but does not give a closed form.






share|cite|improve this answer





















  • This is a special function, theta or something.
    – Did
    Dec 4 at 23:57















up vote
1
down vote



accepted










If I get to choose $a$ I choose $1$ and the sum is $e$.



For $a gt 1$ the sum diverges.



For $0 lt a lt 1$ it will converge quickly but I suspect has no easy answer. Alpha says that for $a=frac 12$ the sum is about $0.531576$ but does not give a closed form.






share|cite|improve this answer





















  • This is a special function, theta or something.
    – Did
    Dec 4 at 23:57













up vote
1
down vote



accepted







up vote
1
down vote



accepted






If I get to choose $a$ I choose $1$ and the sum is $e$.



For $a gt 1$ the sum diverges.



For $0 lt a lt 1$ it will converge quickly but I suspect has no easy answer. Alpha says that for $a=frac 12$ the sum is about $0.531576$ but does not give a closed form.






share|cite|improve this answer












If I get to choose $a$ I choose $1$ and the sum is $e$.



For $a gt 1$ the sum diverges.



For $0 lt a lt 1$ it will converge quickly but I suspect has no easy answer. Alpha says that for $a=frac 12$ the sum is about $0.531576$ but does not give a closed form.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 4 at 20:52









Ross Millikan

290k23195368




290k23195368












  • This is a special function, theta or something.
    – Did
    Dec 4 at 23:57


















  • This is a special function, theta or something.
    – Did
    Dec 4 at 23:57
















This is a special function, theta or something.
– Did
Dec 4 at 23:57




This is a special function, theta or something.
– Did
Dec 4 at 23:57


















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