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A306028 Number of length-n restricted growth strings (RGS) with growth <= four and first element in [4]. 3
1, 4, 26, 214, 2096, 23578, 297692, 4150798, 63148652, 1038505282, 18324165284, 344791676446, 6883214479964, 145160792680210, 3221934217192772, 75022325591768782, 1827426669105650588, 46448931646662304066, 1229212096172351894852, 33800410177112965182910 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..459

FORMULA

E.g.f.: exp(Sum_{j=1..4} (exp(j*x)-1)/j).

MAPLE

b:= proc(n, m) option remember; `if`(n=0, 1,

      add(b(n-1, max(m, j)), j=1..m+4))

    end:

a:= n-> b(n, 0):

seq(a(n), n=0..25);

# second Maple program:

a:= n-> n!*coeff(series(exp(add((exp(j*x)-1)/j, j=1..4)), x, n+1), x, n):

seq(a(n), n=0..25);

CROSSREFS

Column k=4 of A306024.

Cf. A305964.

Sequence in context: A239295 A274735 A283828 * A164101 A048351 A224734

Adjacent sequences:  A306025 A306026 A306027 * A306029 A306030 A306031

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jun 17 2018

STATUS

approved

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Last modified April 9 05:30 EDT 2020. Contains 333343 sequences. (Running on oeis4.)