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 A131926 #28 Apr 20 2017 08:50:14
%S A131926 1,6,78,1266,23010,448062,9140118,192804954,4171347258,92051810934,
%T A131926 2063947865694,46885775086338,1076785174781394,24959959877000238,
%U A131926 583201632981980454,13721408509737851754,324797812150741560618,7729580015834558984934,184829586432121709114478
%N A131926 Expansion of series reversion of x(1-7x)/(1-x).
%C A131926 The Hankel transform of this sequence is 42^C(n+1,2) .
%H A131926 G. C. Greubel, <a href="/A131926/b131926.txt">Table of n, a(n) for n = 1..700</a>
%F A131926 a(n) = Sum_{k=0..n} A086810(n,k)*6^k.
%F A131926 From _Vaclav Kotesovec_, Aug 20 2013: (Start)
%F A131926 G.f.: (x-13-sqrt(x^2-26*x+1))/14.
%F A131926 Recurrence: n*a(n) = 13*(2*n-3)*a(n-1) - (n-3)*a(n-2).
%F A131926 a(n) ~ sqrt(13*sqrt(42)-84)*(13+2*sqrt(42))^n/(14*sqrt(Pi)*n^(3/2)). (End)
%F A131926 G.f.: x/(1 - 6*x/(1 - 7*x/(1 - 6*x/(1 - 7*x/(1 - 6*x/(1 - ...)))))), a continued fraction. - _Ilya Gutkovskiy_, Apr 20 2017
%t A131926 Rest[CoefficientList[InverseSeries[Series[x*(1-7*x)/(1-x),{x,0,20}],x],x]] (* _Vaclav Kotesovec_, Aug 20 2013 *)
%o A131926 (PARI) Vec(serreverse(x*(1-7*x)/(1-x)+O(x^66))) /* _Joerg Arndt_, Feb 06 2013 */
%K A131926 nonn
%O A131926 1,2
%A A131926 _Philippe Deléham_, Oct 29 2007
%E A131926 More terms from _Philippe Deléham_, Feb 06 2013
%E A131926 Offset corrected, _Joerg Arndt_, Feb 15 2013