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 A049827 #10 Aug 08 2021 03:46:20 %S A049827 0,1,3,6,8,13,13,20,22,25,27,38,32,45,45,46,50,63,59,74,64,71,77,96, %T A049827 78,93,99,102,100,125,101,132,122,129,139,136,128,161,157,162,150,187, %U A049827 155,198,176,177,197,224,186,213,211,220,216,257,221,238,222,249 %N A049827 a(n) = T(2n-1,n)+T(2n,n+1)+...+T(3n-3,2n-2) = sum over a period of n-th diagonal of array T given by A049816. %Y A049827 Cf. A049816. %K A049827 nonn %O A049827 1,3 %A A049827 _Clark Kimberling_ %E A049827 More terms from _Sean A. Irvine_, Aug 07 2021