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 A023869 #7 Jun 12 2019 19:15:59 %S A023869 0,1,3,2,4,3,6,10,15,14,19,18,24,23,30,29,37,36,45,54,64,63,74,73,85, %T A023869 84,97,96,110,109,124,123,139,138,154,152,169,167,185,204,224,223,244, %U A023869 243,265,264,287,286,310,309,334,333,359,358,385,383,410,408,436,434,463,461,491,489 %N A023869 a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t is A014306. %K A023869 nonn %O A023869 1,3 %A A023869 _Clark Kimberling_ %E A023869 Title simplified by _Sean A. Irvine_, Jun 12 2019