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 A140303 #10 Nov 14 2021 13:26:39
%S A140303 1,3,1,9,3,1,27,9,3,1,81,27,9,3,1,243,81,27,9,3,1,729,243,81,27,9,3,1,
%T A140303 2187,729,243,81,27,9,3,1,6561,2187,729,243,81,27,9,3,1,19683,6561,
%U A140303 2187,729,243,81,27,9,3,1,59049,19683,6561,2187,729,243,81,27,9,3,1
%N A140303 Triangle T(n,k) = 3^(n-k) read by rows.
%C A140303 Row sums are: 1, 4, 13, 40, 121, 364, .. A003462(n+1).
%D A140303 Advanced Number Theory, Harvey Cohn, Dover Books, 1963, Page 232
%F A140303 T(n,k) = A000244(n-k) . - _R. J. Mathar_, Sep 12 2013
%e A140303 1;
%e A140303 3, 1;
%e A140303 9, 3, 1;
%e A140303 27, 9, 3, 1;
%e A140303 81, 27, 9, 3, 1;
%e A140303 243, 81, 27, 9, 3, 1;
%e A140303 729, 243, 81, 27, 9, 3, 1;
%e A140303 2187, 729, 243, 81, 27, 9, 3, 1;
%e A140303 6561, 2187, 729, 243, 81, 27, 9, 3, 1;
%e A140303 19683, 6561, 2187, 729, 243, 81, 27, 9, 3, 1;
%e A140303 59049, 19683, 6561, 2187, 729, 243, 81, 27, 9, 3, 1;
%t A140303 Clear[p, a] a = 3; p[x, 0] = 1; p[x_, n_] := p[x, n] = Sum[a^i*x^(n - i), {i, 0, n}]; Table[p[x, n], {n, 0, 10}]; a0 = Table[CoefficientList[p[x, n], x], {n, 0, 10}]; Flatten[a0] Table[Apply[Plus, CoefficientList[p[x, n], x]], {n, 0, 10}]
%t A140303 Table[3^(n-k),{n,15},{k,n}]//Flatten (* _Harvey P. Dale_, Nov 14 2021 *)
%Y A140303 Cf. A130321.
%K A140303 nonn,tabl
%O A140303 0,2
%A A140303 _Roger L. Bagula_ and _Gary W. Adamson_, May 27 2008