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 A141396 #8 Nov 26 2016 11:37:36
%S A141396 1,2,3,4,6,9,5,12,18,27,7,15,36,54,81,8,21,45,108,162,243,10,24,63,
%T A141396 135,324,486,729,11,30,72,189,405,972,1458,2187,13,33,90,216,567,1215,
%U A141396 2916,4374,6561,14,39,99,270,648,1701,3645,8748,13122,19683,16,42,117,297
%N A141396 Triangle read by rows, antidiagonals of a multiplication table: 3^n * (numbers not multiples of 3).
%C A141396 Ternary representation of terms in n-th row have n rightmost adjacent zeros.
%C A141396 Row sums = A141397: (1, 5, 19 62, 193, 587, ...).
%H A141396 Ivan Neretin, <a href="/A141396/b141396.txt">Table of n, a(n) for n = 0..5049</a>
%F A141396 Triangle read by rows, descending antidiagonals of the multiplication table: (top row, numbers not multiples of 3); leftmost column, 3^n.
%e A141396 The array begins:
%e A141396 1, 2, 4, 5, 7, ...
%e A141396 3, 6, 12, 15, 21, ...
%e A141396 9, 18, 36, 45, 63, ...
%e A141396 27, 54, 108, 135, 189, ...
%e A141396 81, 162, 324, 405, 567, ...
%e A141396 ...
%e A141396 Descending antidiagonals of the array give
%e A141396 1;
%e A141396 2, 3;
%e A141396 4, 6, 9;
%e A141396 5, 12, 18, 27;
%e A141396 7, 15, 36, 54, 81;
%e A141396 8, 21, 45, 108, 162, 243;
%e A141396 10, 24, 63, 135, 324, 486, 729;
%e A141396 11, 30, 72, 189, 405, 972, 1458, 2187;
%e A141396 ...
%t A141396 Flatten[Table[3^k*Quotient[(3 (m - k) - 1), 2], {m, 0, 10}, {k, 0, m - 1}]] (* _Ivan Neretin_, Nov 26 2016 *)
%Y A141396 Cf. A001651, A141397.
%K A141396 nonn,tabl
%O A141396 0,2
%A A141396 _Gary W. Adamson_, Jun 29 2008