

A118891


Number of binary sequences of length n with no subsequence 01110.


2



1, 2, 4, 8, 16, 31, 60, 116, 223, 428, 820, 1569, 3002, 5744, 10992, 21039, 40273, 77095, 147588, 282538, 540881, 1035440, 1982194, 3794602, 7264164, 13906079, 26620957, 50961552, 97557726, 186758657, 357519595, 684414146, 1310201570
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OFFSET

0,2


COMMENTS

This is a_4(n) in the Doroslovacki reference.


LINKS



FORMULA

Empirical g.f.: (x^8+x^7x^5+2*x^4x+1) / (x^9x^7x^6+4*x^52*x^42*x^2+3*x1).  Colin Barker, Aug 11 2013


PROG

(PARI) { a4(n) = 1 + sum(i=1, n, sum(j=0, ni, sum(k=0, (nij)\2, sum(l=0, (nij2*k)\4, binomial(i1, j)*binomial(i1j, k)*binomial(i1j2*k, l)*binomial(nij2*k3*l+1, l+1))))) }


CROSSREFS



KEYWORD

nonn


AUTHOR

Max Alekseyev, Jun 26 2007


EXTENSIONS



STATUS

approved



