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 A162620 #2 Mar 30 2012 17:34:01 %S A162620 2,2,3,3,4,5,4,5,6,7,7,8,9,10,11,8,9,10,11,12,13,11,12,13,14,15,16,17, %T A162620 12,13,14,15,16,17,18,19,15,16,17,18,19,20,21,22,23,20,21,22,23,24,25, %U A162620 26,27,28,29,21,22,23,24,25,26,27,28,29,30,31,26,27,28,29,30,31,32,33 %N A162620 Triangle read by rows in which row n lists n consecutive natural numbers A000027, starting with A000040(n)-n+1. %C A162620 Note that the last term of the n-th row is the n-th prime A000040(n). %C A162620 See also A162618 and A162619. %e A162620 Triangle begins: %e A162620 .2; %e A162620 .2, 3; %e A162620 .3, 4, 5; %e A162620 .4, 5, 6, 7; %e A162620 .7, 8, 9,10,11; %e A162620 .8, 9,10,11,12,13; %e A162620 11,12,13,14,15,16,17; %e A162620 12,13,14,15,16,17,18,19; %e A162620 15,16,17,18,19,20,21,22,23; %e A162620 20,21,22,23,24,25,26,27,28,29; %e A162620 21,22,23,24,25,26,27,28,29,30,31; %Y A162620 Cf. A000040, A159797, A159798, A162611, A162618, A162619. %K A162620 easy,nonn,tabl %O A162620 1,1 %A A162620 _Omar E. Pol_, Jul 10 2009