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 A247090 #20 Nov 28 2014 21:54:11
%S A247090 1,2,1,1,1,1,2,1,1,1,1,3,1,1,1,2,3,1,1,1,1,1,1,1,5,1,1,1,2,1,1,5,3,1,
%T A247090 1,1,1,1,1,5,3,1,1,1,1,2,1,1,5,3,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,2,3,
%U A247090 1,1,1,1,1,1,1,1,1,1
%N A247090 Eric Rowland's generalization of A132199 as a rectangular array A read by upward antidiagonals.
%C A247090 Conjecture [Rowland] (paraphrased): Let A be the above array with entry A(n,k) in row n and column k. For each n, there exists an index N(n) >= 1 such that A(n,j) is either 1 or prime for all j > N(n).
%H A247090 Eric S. Rowland, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL11/Rowland/rowland21.html">A natural prime-generating recurrence</a>, J. Integer Seq., 11 (2008), Article 08.2.8.
%e A247090 Array A begins:
%e A247090 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
%e A247090 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
%e A247090 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
%e A247090 2, 3, 1, 5, 3, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 1, 3, 1, 5, 3, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 2, 1, 1, 5, 3, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 1, 1, 1, 5, 3, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 2, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 13, ...
%e A247090 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 13, ...
%e A247090 2, 3, 1, 1, 1, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 1, 3, 1, 1, 1, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 2, 1, 1, 1, 1, 1, 1, 1, 1, 11, 3, 1, ...
%e A247090 ...
%t A247090 (* Array A: *)
%t A247090 max := 13; b[n_, 1] := n; b[n_, k_] := b[n, k] = b[n, k - 1] + GCD[k, b[n, k - 1]]; Grid[Transpose[Differences[Transpose[Table[b[n, k], {n, max}, {k, max}]]]]]
%t A247090 (* Array antidiagonals flattened: *)
%t A247090 max := 13; b[n_, 1] := n; b[n_, k_] := b[n, k] = b[n, k - 1] + GCD[k, b[n, k - 1]]; Flatten[Table[Transpose[Differences[Transpose[Table[b[n, k], {n, max}, {k, max}]]]][[n - k + 1]][[k]], {n, max - 1}, {k, n}]]
%Y A247090 Cf. A106108, A132199, A137613.
%K A247090 nonn,tabl
%O A247090 1,2
%A A247090 _L. Edson Jeffery_, Nov 18 2014