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 A084410 #5 Dec 05 2013 19:56:17 %S A084410 1,2,5,4,13,10,31,20,30,42,61,55,109,70,88,108,181,126,277,148,174, %T A084410 201,397,225,255,287,318,348,547,382,733,417,456,496,535,576,947,621, %U A084410 666,711,1213,758,1499,805,858,910,1831,963,1020,1078,1137,1195,2207,1255 %N A084410 First column of triangle A084408. %C A084410 a(n) is prime iff n is prime. %F A084410 For n prime, a(n) = p(A034387(n)-n+1). For n composite, a(n) = A002808([n*(n+1)/2]-A034387(n)-n). %Y A084410 Cf. A084408, A084409, A084411. %K A084410 nonn,easy %O A084410 1,2 %A A084410 _Amarnath Murthy_, Jun 01 2003 %E A084410 Edited and extended by _David Wasserman_, Dec 27 2004