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 A257943 #11 Jun 10 2015 06:42:38
%S A257943 1,2,2,5,5,3,14,14,8,4,41,41,23,11,5,122,122,68,32,14,6,365,365,203,
%T A257943 95,41,17,7,1094,1094,608,284,122,50,20,8,3281,3281,1823,851,365,149,
%U A257943 59,23,9,9842,9842,5468,2552,1094,446,176,68,26,10
%N A257943 Array A read by upward antidiagonals in which the entry in row n and column k is defined by A(n,k) = (1 + 3^(n-1)*(2*k - 1))/2, n,k >= 1.
%e A257943 Array A begins:
%e A257943 . 1 2 3 4 5 6 7 8 9 10
%e A257943 . 2 5 8 11 14 17 20 23 26 29
%e A257943 . 5 14 23 32 41 50 59 68 77 86
%e A257943 . 14 41 68 95 122 149 176 203 230 257
%e A257943 . 41 122 203 284 365 446 527 608 689 770
%e A257943 . 122 365 608 851 1094 1337 1580 1823 2066 2309
%e A257943 . 365 1094 1823 2552 3281 4010 4739 5468 6197 6926
%e A257943 . 1094 3281 5468 7655 9842 12029 14216 16403 18590 20777
%e A257943 . 3281 9842 16403 22964 29525 36086 42647 49208 55769 62330
%e A257943 . 9842 29525 49208 68891 88574 108257 127940 147623 167306 186989
%t A257943 (* Array: *)
%t A257943 Grid[Table[(1 + 3^(n - 1)*(2*k - 1))/2, {n, 10}, {k, 10}]]
%t A257943 (* Array antidiagonals flattened: *)
%t A257943 Flatten[Table[(1 + 3^(n - k)*(2*k - 1))/2, {n, 10}, {k, n}]]
%Y A257943 Cf. A191450, A254051.
%K A257943 nonn,tabl
%O A257943 1,2
%A A257943 _L. Edson Jeffery_, May 13 2015