This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A287617 #17 Mar 25 2023 08:10:31 %S A287617 1,1,1,1,5,21,61,141,309,766,2191,6436,18041,48348,128311,347166, %T A287617 960197,2674883,7413514,20411986,56130675,154907229,429349768, %U A287617 1192532452,3312339849,9196063371,25538113056,70994900341,197595884071,550414483911,1533911418946 %N A287617 Main diagonal of A045847. %C A287617 a(n) is the number of representations of n as a sum of n squares of nonnegative integers. %H A287617 Seiichi Manyama, <a href="/A287617/b287617.txt">Table of n, a(n) for n = 0..500</a> %F A287617 a(n) = [x^n] (1 + theta_3(x))^n/2^n, where theta_() is the Jacobi theta function. - _Ilya Gutkovskiy_, Jan 17 2018 %F A287617 a(n) ~ c * d^n / sqrt(n), where d = 2.83312434251238... and c = 0.229098651125... - _Vaclav Kotesovec_, Mar 25 2023 %Y A287617 Cf. A045847. %K A287617 nonn %O A287617 0,5 %A A287617 _Seiichi Manyama_, May 28 2017