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 A062107 #16 Apr 25 2024 09:10:19
%S A062107 0,1,3,10,30,90,270,810,2430,7290,21870,65610,196830,590490,1771470,
%T A062107 5314410,15943230,47829690,143489070,430467210,1291401630,3874204890,
%U A062107 11622614670,34867844010,104603532030,313810596090,941431788270
%N A062107 Diagonal of table A062104.
%H A062107 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3).
%F A062107 a(n) = 10*3^(n-4) for n >= 4.
%F A062107 From _Paul Barry_, Oct 15 2004: (Start)
%F A062107 G.f.: x^2(1+x^2)/(1-3x);
%F A062107 a(n) = Sum_{k=0..n-2} 3^(n-k-2)binomial(1, k/2)(1+(-1)^k)/2. (End)
%p A062107 [seq(ChessPawnTriangle(j,j),j=1..50)];
%Y A062107 Except for initial terms, same as A005052.
%K A062107 nonn
%O A062107 1,3
%A A062107 _Antti Karttunen_, May 30 2001