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 A369734 #7 Jan 30 2024 20:09:59 %S A369734 0,1,1,1,1,3,8,17,35,79,177,409,995,2475,6336,16078,41401,107304, %T A369734 279550,736032,1950000,5199850,13950852,37576658,101670863,276228026, %U A369734 753114256,2060995699,5658663542,15583477334,43039552072,119179072495,330836308272,920537185436 %N A369734 Number of solutions to 1^2*k_1 + 2^2*k_2 + ... + n^2*k_n = 1, where k_i are from {-1,0,1}, i=1..n. %F A369734 a(n) = [x^1] Product_{k=1..n} (x^(k^2) + 1 + 1/x^(k^2)). %t A369734 Table[Coefficient[Product[(x^(k^2) + 1 + 1/x^(k^2)), {k, 1, n}], x, 1], {n, 0, 32}] %Y A369734 Cf. A007576, A063866, A350249, A369433, A369628, A369735. %K A369734 nonn %O A369734 0,6 %A A369734 _Ilya Gutkovskiy_, Jan 30 2024