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 A132866 #13 May 11 2019 02:21:08
%S A132866 1,6,78,1308,24942,513876,11148012,250917624,5805563310,137233668900,
%T A132866 3299955883428,80468668049160,1985171406618156,49458290358431688,
%U A132866 1242613072013591832,31448339835422435568
%N A132866 Expansion of 1/(1-6x*c(7x)), where c(x) is the g.f. of A000108.
%F A132866 G.f.: 7/(4 + 3*sqrt(1-28*x)).
%F A132866 a(n) = 7^n*Sum_{j=0..n} (6/7)^j*j*binomial(2n-j,n)/(2n-j) for n >= 1. - _Emeric Deutsch_, Nov 19 2007
%F A132866 a(n) = Sum_{k=0..n} A039599(n,k)*(-1)^k*7^(n-k). - _Philippe Deléham_, Dec 11 2007
%p A132866 g:=7/(4+3*sqrt(1-28*x)): gser:=series(g,x=0,18): seq(coeff(gser,x,n),n=0..15); # _Emeric Deutsch_, Nov 19 2007
%K A132866 nonn
%O A132866 0,2
%A A132866 _Philippe Deléham_, Nov 18 2007
%E A132866 More terms from _Emeric Deutsch_, Nov 19 2007