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Search: id:A118891
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| A118891 |
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Number of binary sequences of length n with no subsequence 01110. |
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+0
3
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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
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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This is a_4(n) in the Doroslovacki reference.
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LINKS
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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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PROGRAM
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(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
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Cf. A000045, A005251, A049864.
Sequence in context: A106399 A007800 A102726 this_sequence A107066 A006775 A104993
Adjacent sequences: A118888 A118889 A118890 this_sequence A118892 A118893 A118894
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KEYWORD
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nonn
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AUTHOR
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Max Alekseyev, Jun 26 2007
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