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A118891
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Number of binary sequences of length n with no subsequence 01110.
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2
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| This is a_4(n) in the Doroslovacki reference.
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LINKS
| R. Doroslovacki, Binary sequences without 011...110 (k-1 1's) for fixed k, Mat. Vesnik 46 (1994), no. 3-4, 93-98.
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PROG
| (PARI) { a4(n) = 1 + sum(i=1, n, sum(j=0, n-i, sum(k=0, (n-i-j)\2, sum(l=0, (n-i-j-2*k)\4, binomial(i-1, j)*binomial(i-1-j, k)*binomial(i-1-j-2*k, l)*binomial(n-i-j-2*k-3*l+1, l+1))))) }
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CROSSREFS
| Cf. A000045, A005251, A049864.
Sequence in context: A188900 A189075 A189077 * A107066 A141019 A152718
Adjacent sequences: A118888 A118889 A118890 * A118892 A118893 A118894
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KEYWORD
| nonn
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AUTHOR
| Max Alekseyev, Jun 26 2007
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EXTENSIONS
| More terms from Max Alekseyev (maxale(AT)gmail.com), Sep 25 2009
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