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Search: id:A077608
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| A077608 |
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Number of compositions of n into twin primes (i.e. primes that are members of a twin prime pair, like 3,5,7,11,13, but not 2 or 23). |
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+0
2
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| 1, 0, 0, 1, 0, 1, 1, 1, 2, 1, 3, 4, 3, 7, 7, 8, 14, 15, 21, 28, 33, 47, 58, 75, 103, 125, 167, 220, 275, 370, 474, 610, 806, 1028, 1347, 1752, 2253, 2954, 3812, 4944, 6451, 8329, 10841, 14077, 18226, 23720, 30745, 39903, 51857, 67214, 87313
(list; graph; listen)
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OFFSET
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0,9
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LINKS
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P. Flajolet, Publications
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FORMULA
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A77608 := proc(n) coeff(series(1/(1-add(z^numtheory[ithprime](j)* subs([true=1, false=0], evalb(isprime(ithprime(j)-2) or isprime(ithprime(j)+2))), j=2..n+2)), z=0, n+1), z, n): end;
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EXAMPLE
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a(15)=8 since 15=11+7=7+11=5+13=13+5=3+5+7=3+7+5=5+3+7=5+7+3=7+3+5=7+5+3, and 3,5,7,11 belong to twin pairs.
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MAPLE
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A077608 := proc(n) coeff(series(1/(1-add(z^numtheory[ithprime](j)* subs([true=1, false=0], evalb(isprime(ithprime(j)-2) or isprime(ithprime(j)+2))), j=2..n+2)), z=0, n+1), z, n): end;
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CROSSREFS
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Cf. A002124, A023360.
Sequence in context: A122530 A022466 A133310 this_sequence A002124 A097564 A128270
Adjacent sequences: A077605 A077606 A077607 this_sequence A077609 A077610 A077611
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KEYWORD
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nonn
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AUTHOR
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Philippe Flajolet (Philippe.Flajolet(AT)inria.fr), Nov 11 2002
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