cp's OEIS Frontend

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.

A173108 Triangle, A000110 in every column > 0, shifted down twice.

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%I A173108 #11 Nov 19 2022 15:55:38
%S A173108 1,1,2,1,5,1,15,2,1,52,5,1,203,15,2,1,877,52,5,1,4140,203,15,2,1,
%T A173108 21147,877,52,5,1,115975,4140,203,15,2,1,678570,21147,877,52,5,1,
%U A173108 4213597,115975,4140,203,15,2,1,27644437,678570,21147,877,52,5,1
%N A173108 Triangle, A000110 in every column > 0, shifted down twice.
%C A173108 Row sums = A173109: (1, 1, 3, 6, 18, 58, 221, 935, ...).
%C A173108 Let the triangle = M. Then lim_{n->oo} M^n = A173110: (1, 1, 3, 6, 20, 60, ...).
%F A173108 Bell sequence in every column, for columns > 0, shifted down twice.
%e A173108 First few rows of the triangle:
%e A173108        1;
%e A173108        1;
%e A173108        2,    1;
%e A173108        5,    1;
%e A173108       15,    2,   1;
%e A173108       52,    5,   1;
%e A173108      203,   15,   2,  1;
%e A173108      877,   52,   5,  1;
%e A173108     4140,  203,  15,  2, 1;
%e A173108    21147,  877,  52,  5, 1;
%e A173108   115975, 4140, 203, 15, 2, 1;
%e A173108   ...
%t A173108 T[n_, k_] := BellB[n - 2 k];
%t A173108 Table[T[n, k], {n, 0, 10}, {k, 0, Quotient[n, 2]}] // Flatten (* _Jean-François Alcover_, Apr 22 2022 *)
%o A173108 (PARI) B(n) = sum(k=0, n, stirling(n, k, 2)); \\ A000110
%o A173108 tabf(nn) = for (n=0, nn, for(k=0, n\2, print1(B(n-2*k), ", "));); \\ _Michel Marcus_, Nov 19 2022
%Y A173108 Cf. A000110, A173109, A173110, A173111.
%K A173108 nonn,tabf
%O A173108 0,3
%A A173108 _Gary W. Adamson_, Feb 09 2010
%E A173108 Keyword tabf and more terms from _Michel Marcus_, Nov 19 2022