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Search: id:A109903
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| A109903 |
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Let c = composite(n) & p = prime(n); a(n) = binomial( max(c,p), min(c,p) ). |
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+0
1
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| 6, 20, 56, 36, 11, 13, 680, 3876, 245157, 34597290, 84672315, 12875774670, 244662670200, 800472431850, 14833897694226, 973469712824056, 48402641245296107, 191724747789809255, 9989690752182277136
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OFFSET
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1,1
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COMMENT
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11 and 13 are the only prime terms. For a(7) onwards sequence is monotonically increasing.
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EXAMPLE
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a(3) = C(8,5) = 56, a(8) = C(19,15) =3876.
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MATHEMATICA
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Composite[ n_Integer ] := Block[{k = n + PrimePi[ n ] + 1}, While[ k != n + PrimePi[ k ] + 1, k++ ]; k]; f[n_] := Block[{a = Sort[{Composite[n], Prime[n]}]}, Binomial[Last[a], First[a]]]; Table[ f[n], {n, 19}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Jul 16 2005)
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CROSSREFS
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Sequence in context: A028492 A059822 A152959 this_sequence A014480 A048778 A048611
Adjacent sequences: A109900 A109901 A109902 this_sequence A109904 A109905 A109906
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KEYWORD
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easy,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 14 2005
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Jul 16 2005
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