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 A164678 #2 Mar 31 2012 13:23:39 %S A164678 1,2,1,5,4,2,9,8,6,2,17,16,14,9,3,28,27,25,20,12,3,47,46,44,39,30,16, %T A164678 4,73,72,70,65,56,40,20,4,114,113,111,106,97,80,55,25,5,170,169,167, %U A164678 162,153,136,109,70,30,5,253,252,250,245,236,219,191,147,91,36,6,365 %N A164678 Convolve A008619 with sequences which map to 2,3,5,7,11,13,17... A000040 then, by bending when needed, summarize the results in a triangular array. %C A164678 Sequence A164680 is not in the triangle since 45 = 3*15 and 15 is not a member of A000040 (the prime numbers). %e A164678 The desired triangle begins: %e A164678 .1 %e A164678 .2..1 %e A164678 .5..4..2 %e A164678 .9..8..6..2 %e A164678 17.16.14..9..3 %e A164678 28.27.25.20.12..3 %e A164678 47.46.44.39.30.16..4 %e A164678 etc. %e A164678 Note that 21 = 3*7 maps to 1,2,5,9,17,27,44,... A139672 is embedded in the triangle. %Y A164678 Cf. A008619 A002620 A006918 A097701 A139672 ... A000097 (embedded sequences). %K A164678 nonn,tabl,uned %O A164678 1,2 %A A164678 _Alford Arnold_, Aug 25 2009