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 A219795 #9 Jan 06 2013 15:19:07 %S A219795 2,2,2,2,3,3,5,7,10,11,16,23,33,44,58,81,114,158,212,293,407,565,777, %T A219795 1064,1471,2036,2813,3863,5334,7370,10183,14046,19356,26726,36909, %U A219795 50955,70251,96977,133886,184841,255092 %N A219795 Sum of the absolute values of the antidiagonals of the triangle A135929(n) companion. See the comment. %C A219795 The companion to A135929(n) is the triangle %C A219795 2; %C A219795 2, 0; %C A219795 2, 0, 1; %C A219795 2, 0, -1, 0; %C A219795 2, 0, -3, 0, -1; %C A219795 2, 0, -5, 0, 0, 0; %C A219795 2, 0, -7, 0, 3, 0, 1; %C A219795 2, 0, -9, 0, 8, 0, 1, 0; %C A219795 (A192011(n) beginning with 2 instead of -1). %C A219795 Consider a(1),a(5),a(10),a(14), that is, a(A193910(n) -1). %C A219795 a(1)+a(4)-a(5) = 2, a(5)+a(8)-a(9) = 2, a(10)+a(13)-a(14) = 2, a(14)+a(17)-a(18) = 4, a(19)+a(22)-a(23) = 6, a(23)+a(26)-a(27) = 14, yields 2,2,2,4,6,14,24,60,... = 2*A047749(n) or 2, followed with A116637(n+1). %F A219795 a(n) = sum abs ( [k=0..floor(n/2)] A192011(n-k,k) ), a(0)=2. %e A219795 a(0)=2, a(1)=2, a(2)=2+0, a(3)=2+0, a(4)=2+0+1, a(5)=2+0+1. %p A219795 A219795 := proc(n) %p A219795 if n=0 then %p A219795 2; %p A219795 else %p A219795 add(abs(A192011(n-k,k)),k=0..floor(n/2)) ; %p A219795 end if; %p A219795 end proc: # _R. J. Mathar_, Jan 06 2013 %K A219795 nonn %O A219795 0,1 %A A219795 _Paul Curtz_, Nov 28 2012 %E A219795 a(24)-a(40) from Jean-Francois Alcover, Nov 28 2012