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 A306942 #16 Sep 25 2019 16:42:33
%S A306942 1,9,45,165,495,1287,3003,6435,12870,24309,43740,75411,124830,197505,
%T A306942 293436,389367,389367,0,-1562274,-6216183,-18365697,-47600136,
%U A306942 -113879520,-257123889,-554298228,-1148646906,-2297293812,-4443424371,-8313049440,-15011769204
%N A306942 Expansion of 1/((1 - x)^9 + x^9).
%H A306942 Seiichi Manyama, <a href="/A306942/b306942.txt">Table of n, a(n) for n = 0..3000</a>
%H A306942 <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 A306942 a(n) = Sum_{k=0..floor(n/9)} (-1)^k*binomial(n+8,9*k+8).
%F A306942 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 > 7.
%t A306942 CoefficientList[Series[1/((1-x)^9+x^9),{x,0,30}],x] (* _Harvey P. Dale_, Sep 25 2019 *)
%o A306942 (PARI) {a(n) = sum(k=0, n\9, (-1)^k*binomial(n+8, 9*k+8))}
%o A306942 (PARI) N=66; x='x+O('x^N); Vec(1/((1-x)^9+x^9))
%Y A306942 Column 9 of A306914.
%Y A306942 Cf. A306939.
%K A306942 sign,easy
%O A306942 0,2
%A A306942 _Seiichi Manyama_, Mar 17 2019