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 A247936 #8 Oct 09 2014 18:54:09
%S A247936 1,1,2,3,2,4,9,6,4,8,27,18,12,8,16,81,54,36,24,16,32,243,162,108,72,
%T A247936 48,32,64,729,486,324,216,144,96,64,128,2187,1458,972,648,432,288,192,
%U A247936 128,256,6561,4374,2916,1944,1296,864,576,384,256,512,19683,13122
%N A247936 Riordan array ((1-2x)/(1-3x), 2x).
%C A247936 Mirror of A153279.
%F A247936 Sum_{k, 0<=k<=n} T(n,k) = 3^n = A000244(n).
%F A247936 T(n,k) = A133494(n-k)*2^k.
%F A247936 T(2n,n) = A167747(n).
%e A247936 Triangle begins:
%e A247936 1
%e A247936 1, 2
%e A247936 3, 2, 4
%e A247936 9, 6, 4, 8
%e A247936 27, 18, 12, 8, 16
%e A247936 81, 54, 36, 24, 16, 32
%e A247936 243, 162, 108, 72, 48, 32, 64
%e A247936 Production matrix begins:
%e A247936 1, 2
%e A247936 1, 0, 2
%e A247936 1, 0, 0, 2
%e A247936 1, 0, 0, 0, 2
%e A247936 1, 0, 0, 0, 0, 2
%e A247936 1, 0, 0, 0, 0, 0, 2
%e A247936 1, 0, 0, 0, 0, 0, 0, 2
%Y A247936 Cf. A000079, A000244, A133494, A153279, A167747.
%K A247936 nonn,tabl
%O A247936 0,3
%A A247936 _Philippe Deléham_, Sep 26 2014