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 A258936 #25 Aug 10 2023 03:01:09
%S A258936 -1,-3,7,-15,89,-63,121,-255,3521,-13119,18273,-4095,-40319,-16383,
%T A258936 425089,-2676735,6141953,-262143,-22487551,-1048575,173791233,
%U A258936 -356171775,176138241,-16777215,2378907649,-5430575103,3355336705,-38913703935,164745740289,-1073741823,-770681831423,-4294967295,4113638096897,-3796520402943,1133869137921,-38542231207935,87257121292289,-274877906943
%N A258936 G.f.: Sum_{n=-oo..+oo} x^n * (1 - 2^n*x^n)^n.
%C A258936 Compare to the curious identity: Sum_{n=-oo..+oo} x^n * (1 - x^n)^n = 0.
%C A258936 More generally, for all k we have the identity:
%C A258936 Sum_{n=-oo..+oo} x^n * (1 - k^n*x^n)^n = (-1) * Sum_{n=-oo..+oo} k*(k*x)^n * (1 - k*(k*x)^n)^n. - _Paul D. Hanna_, Dec 25 2015
%H A258936 Paul D. Hanna, <a href="/A258936/b258936.txt">Table of n, a(n) for n = 0..500</a>
%F A258936 G.f.: (-1) * Sum_{n=-oo..+oo} 2*(2*x)^n * (1 - 2*(2*x)^n)^n. - _Paul D. Hanna_, Dec 25 2015
%F A258936 It appears that for prime p >= 3, a(p) = 1 - 2^(p+1). - _Peter Bala_, Aug 06 2023
%e A258936 G.f.: A(x) = -1 - 3*x + 7*x^2 - 15*x^3 + 89*x^4 - 63*x^5 + 121*x^6 - 255*x^7 + 3521*x^8 - 13119*x^9 + 18273*x^10 - 4095*x^11 - 40319*x^12 + ...
%o A258936 (PARI) {a(n) = local(A=1); A = sum(k=-sqrtint(n)-1, n+1, x^k*(1 - 2^k*x^k + x*O(x^n))^k ); polcoeff(A, n)}
%o A258936 for(n=0, 60, print1(a(n), ", "))
%Y A258936 Cf. A260147.
%K A258936 sign
%O A258936 0,2
%A A258936 _Paul D. Hanna_, Nov 06 2015