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 A091881 #19 Jun 01 2020 07:40:16
%S A091881 1,6,86,1366,21846,349526,5592406,89478486,1431655766,22906492246,
%T A091881 366503875926,5864062014806,93824992236886,1501199875790166,
%U A091881 24019198012642646,384307168202282326,6148914691236517206
%N A091881 Expansion of (1-11x)/((1-x)(1-16x)).
%C A091881 With interpolated zeros, this is the multinomial expression sum{i=0..n,sum{j=0..n,sum{k=0..n,if (mod(n-2i-4j-4k,6)=0,n!/(i!j!k!(n-i-j-k)!),0)}}}. Binomial transform of A091882.
%H A091881 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (17,-16).
%F A091881 a(n) = 16^n/3 + 2/3; a(n) = A001045(4*n) + 1.
%F A091881 a(0)=1, a(1)=6, a(n) = 17*a(n-1) - 16*a(n-2) [_Harvey P. Dale_, Dec 15 2011]
%F A091881 a(n) = A078008(4n). - _Oboifeng Dira_, May 29 2020
%t A091881 CoefficientList[Series[(1-11x)/((1-x)(1-16x)),{x,0,30}],x] (* or *) LinearRecurrence[{17,-16},{1,6},30] (* _Harvey P. Dale_, Dec 15 2011 *)
%Y A091881 Cf. A001045, A078008, A091882.
%K A091881 easy,nonn
%O A091881 0,2
%A A091881 _Paul Barry_, Feb 10 2004