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 A307045 #17 May 26 2021 00:56:05
%S A307045 1,1,1,1,1,1,1,1,1,0,-9,-54,-219,-714,-2001,-5004,-11439,-24309,
%T A307045 -48618,-92358,-167769,-292599,-490104,-783540,-1172907,-1562274,
%U A307045 -1562274,0,6216183,24581880,72182016,186061536,443185425,997483653,2146130559,4443424371,8886848742
%N A307045 a(n) = Sum_{k=0..floor(n/9)} (-1)^k*binomial(n,9*k).
%H A307045 Seiichi Manyama, <a href="/A307045/b307045.txt">Table of n, a(n) for n = 0..3000</a>
%H A307045 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (9,-36,84,-126,126,-84,36,-9).
%F A307045 G.f.: (1 - x)^8/((1 - x)^9 + x^9).
%F A307045 a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) for n > 8.
%t A307045 a[n_] := Sum[(-1)^k * Binomial[n,9*k], {k,0,Floor[n/9]}]; Array[a, 37, 0] (* _Amiram Eldar_, May 25 2021 *)
%o A307045 (PARI) {a(n) = sum(k=0, n\9, (-1)^k*binomial(n, 9*k))}
%o A307045 (PARI) N=66; x='x+O('x^N); Vec((1-x)^8/((1-x)^9+x^9))
%Y A307045 Column 9 of A307039.
%Y A307045 Cf. A306860.
%K A307045 sign,easy
%O A307045 0,11
%A A307045 _Seiichi Manyama_, Mar 21 2019