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A131283 a(n) is the number of binary strings of length n such that there exist 3 or more ones in a subsequence of length 5 or less. 0
0, 0, 1, 5, 16, 38, 85, 185, 396, 838, 1748, 3609, 7400, 15097, 30681, 62154, 125588, 253246, 509850, 1025153, 2059159, 4132679, 8288643, 16615051, 33291367, 66682128, 133525499, 267312553, 535049374, 1070786975, 2142690382 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..31.

FORMULA

a(n) = 2^n - A120118.

a(n)= +3*a(n-1) -2*a(n-2) +a(n-3) -2*a(n-4) +2*a(n-5) -4*a(n-6) -a(n-8) +2*a(n-9) -a(n-10) +2*a(n-11).

G.f. x^3*(-1-2*x-3*x^2+x^6+x^7+x^3+2*x^5) / ( (2*x-1)*(x^10+x^8-2*x^5-x^3-x+1) ). - R. J. Mathar, Nov 28 2011

CROSSREFS

Cf. A118647, A118646.

Sequence in context: A211807 A174723 A011932 * A082199 A082190 A155965

Adjacent sequences:  A131280 A131281 A131282 * A131284 A131285 A131286

KEYWORD

nonn

AUTHOR

Tanya Khovanova, Sep 28 2007

STATUS

approved

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Last modified August 21 17:33 EDT 2017. Contains 290891 sequences.