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 A255544 #12 Mar 15 2016 05:10:03
%S A255544 2,5,4,19,11,6,27,39,17,8,45,57,61,23,10,55,97,91,81,29,12,85,117,147,
%T A255544 121,103,35,14,109,177,181,199,153,123,41,16,139,225,277,243,253,183,
%U A255544 145,47,18,157,295,345,369,315,301,217,165,53,20,175,325,447,465,471,379,351,247,187,59,22,213,381,493,603,589,567,441,403,279,207,65,24
%N A255544 Unlucky array, transposed.
%C A255544 See comments at A255543.
%H A255544 Antti Karttunen, <a href="/A255544/b255544.txt">Table of n, a(n) for n = 1..5886; the first 108 antidiagonals of the array, flattened</a>
%t A255544 rows = cols = 12; L = 2 Range[0, 2000] + 1; A = Join[{2 Range[cols]}, Reap[For[n = 2, n <= rows, r = L[[n++]]; L0 = L; L = ReplacePart[L, Table[r i -> Nothing, {i, 1, Length[L]/r}]]; Sow[Complement[L0, L][[1 ;; cols]]]]][[2, 1]]]; Table[A[[n - k + 1, k]], {n, 1, Min[rows, cols]}, {k, 1, n}] // Flatten (* _Jean-François Alcover_, Mar 15 2016 *)
%o A255544 (Scheme) (define (A255544 n) (A255543bi (A004736 n) (A002260 n))) ;; Other code as in A255543.
%Y A255544 Transpose: A255543.
%Y A255544 Permutation of A050505.
%K A255544 nonn,tabl
%O A255544 1,1
%A A255544 _Antti Karttunen_, Feb 25 2015