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A007558 Shifts 2 places left when e.g.f. is squared.
(Formerly M1230)
2
1, 1, 1, 2, 4, 10, 30, 100, 380, 1600, 7400, 37400, 204600, 1205600, 7612000, 51260000, 366784000, 2778820000, 22222332000, 187067320000, 1653461480000, 15310662400000, 148217381840000, 1497226615280000, 15754506226800000, 172407188412800000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..200

M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210.

FORMULA

a(n) ~ c * d^n * n! * n, where d = 0.42089835222875..., c = 1.06293253745... . - Vaclav Kotesovec, Sep 06 2014

MAPLE

a:= proc(n) option remember;

      `if`(n<2, 1, add(a(i)*a(n-2-i) *binomial(n-2, i), i=0..n-2))

    end:

seq (a(n), n=0..30);  # Alois P. Heinz, Jun 22 2012

MATHEMATICA

a[n_] := a[n] = If[n<2, 1, Sum[a[i]*a[n-2-i]*Binomial[n-2, i], {i, 0, n-2}]]; Table[a[n], {n, 0, 30}] (* Jean-Fran├žois Alcover, Feb 03 2014, after Alois P. Heinz *)

CROSSREFS

Sequence in context: A149836 A003289 A087161 * A094957 A000733 A092073

Adjacent sequences:  A007555 A007556 A007557 * A007559 A007560 A007561

KEYWORD

nonn,nice,eigen

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 26 20:33 EST 2014. Contains 250119 sequences.