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 A136103 #5 Oct 06 2015 11:48:29 %S A136103 1,2,4,6,12,8,24,30,36,60,72,120,180,360,16,48,144,210,216,240,420, %T A136103 432,720,840,900,1080,1260,1680,1800,2160,2520,3600,5040,5400,6300, %U A136103 7560,10800,12600,15120,25200,37800,75600 %N A136103 A Catalan shaped array (A000245) of least prime signatures (A025487) based on staircase Ferrers boards; cf. A136102. %e A136103 The array begins %e A136103 1 %e A136103 2 %e A136103 4...6..12 %e A136103 8..24..30..36..60..72..120..180..360 %e A136103 16... %e A136103 with 1 1 3 9 28 90 ... least prime signatures per row; %e A136103 hence there are 1 2 5 14 42 132 ... Catalan objects counted. %e A136103 The staircases can be coded 1 2 12 360 75600 174636000 ...: A006939. %e A136103 There are 14 signatures dividing 360; but 5 of these also divide 12 so there are nine new signatures: 8..24..30..36..60..72..120..180..360 %Y A136103 Cf. A000108, A000245, A006939, A025487, A136102. %K A136103 easy,tabf,nonn %O A136103 0,2 %A A136103 _Alford Arnold_, Jan 12 2008