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 A027910 #22 Aug 25 2014 11:11:50
%S A027910 1,6,36,210,1221,7098,41328,241128,1409895,8260934,48497064,285219090,
%T A027910 1680166215,9912297150,58558256496,346371955776,2051126447742,
%U A027910 12158963346852,72147074769640,428476010502582,2546776668682323,15149061841758174,90175327717962024
%N A027910 T(2n,n-2), T given by A027907.
%C A027910 a(n) is also the number of lattice paths from (0,0) to (2n-1,n-2) taking north and east steps avoiding north^{>=3}. - _Shanzhen Gao_, Apr 20 2010
%H A027910 Alois P. Heinz, <a href="/A027910/b027910.txt">Table of n, a(n) for n = 2..500</a>
%F A027910 a(n) = Sum_{i=0..floor((2*n-3)/2)} C(2*n,n-2-i)*C(n-2-i,i). _Shanzhen Gao_, Apr 20 2010
%F A027910 G.f.: -g^2*(g^2+g+1)/(3*g^2+g-1) where g = x times the g.f. of A143927. - _Mark van Hoeij_, Nov 16 2011
%F A027910 a(n) ~ sqrt((221-29*sqrt(13))/78) * ((70+26*sqrt(13))/27)^n/(9*sqrt(Pi*n)). - _Vaclav Kotesovec_, Aug 25 2014
%p A027910 a:= proc(n) option remember; `if`(n<3, n*(n-1)/2,
%p A027910 (14*(2*n-1)*(65*n^3-120*n^2+37*n+6) *a(n-1)
%p A027910 +36*(n-1)*(2*n-1)*(2*n-3)*(13*n+2) *a(n-2))/
%p A027910 (3*(13*n-11)*(n-2)*(3*n+2)*(3*n+1)))
%p A027910 end:
%p A027910 seq(a(n), n=2..25); # _Alois P. Heinz_, Aug 07 2013
%K A027910 nonn
%O A027910 2,2
%A A027910 _Clark Kimberling_