A284720 - OEIS

A284720

Number of indecomposable permutations avoiding the vincular pattern 1 2_ 3_.

1, 1, 3, 11, 43, 179, 801, 3861, 19991, 110679, 652127, 4071179, 26823449, 185864737, 1350279523, 10256563803, 81258332915, 669990127123, 5737790656217, 50947129880373, 468260045596695, 4448381809651895, 43618802110132167, 440918949811405787

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..24.

A. L. L. Gao, S. Kitaev, P. B. Zhang. On pattern avoiding indecomposable permutations, arXiv:1605.05490 [math.CO], 2016.

MATHEMATICA

Table[BellB[n] - Sum[BellB[k], {k, 0, n-2}], {n, 1, 30}] (* Vaclav Kotesovec, Apr 02 2017 *)

PROG

(Python)

from sympy import bell

print([bell(n) - sum(bell(k) for k in range(n - 1)) for n in range(1, 30)]) # Indranil Ghosh, Apr 03 2017 (translated from Mathematica)

CROSSREFS

Sequence in context: A196151 A149071 A149072 * A151096 A151097 A151098

Adjacent sequences: A284717 A284718 A284719 * A284721 A284722 A284723

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Apr 02 2017

EXTENSIONS

More terms from Vaclav Kotesovec, Apr 02 2017

STATUS

approved