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A094536
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Number of binary words of length n that are not "bifix-free".
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3
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0, 0, 2, 4, 10, 20, 44, 88, 182, 364, 740, 1480, 2980, 5960, 11960, 23920, 47914, 95828, 191804, 383608, 767500, 1535000, 3070568, 6141136, 12283388, 24566776, 49135784, 98271568, 196547560, 393095120, 786199088, 1572398176, 3144813974
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| Equals 2^n - A003000(n).
Let b(0)=1; b(n)=2*b(n-1)-1/2*(1+(-1)^n)*b([n/2]); a(n)=2^n-b(n). - Farideh Firoozbakht (mymontain(AT)yahoo.com), Jun 10 2004
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MATHEMATICA
| b[0]=1; b[n_]:=b[n]=2*b[n-1]-(1+(-1)^n)/2*b[Floor[n/2]]; a[n_]:=2^n-b[n]; Table[a[n], {n, 0, 34}]
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CROSSREFS
| See A003000 for much more information. Cf. A094537.
Sequence in context: A167193 A026666 A121880 * A003407 A151523 A026395
Adjacent sequences: A094533 A094534 A094535 * A094537 A094538 A094539
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 06 2004
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EXTENSIONS
| More terms from Farideh Firoozbakht (mymontain(AT)yahoo.com), Jun 10 2004
Corrected by Don Rogers (donrogers42(AT)aol.com), Feb 15 2005
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