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Search: id:A117927
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| A117927 |
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Binomial coefficient C[s(n), n] where s(n) = n-th semiprime. |
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+0
1
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| 4, 15, 84, 210, 2002, 5005, 116280, 319770, 2042975, 5311735, 193536720, 548354040, 1476337800, 9669554100, 25140840660, 991493848554, 6499270398159, 27900908274925, 280576272201225, 1210269541711230, 3342649210440540
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OFFSET
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1,1
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COMMENT
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Semiprime analogue of A060604 Binomial coefficient C[p(n), n] where p(n) = n-th prime.
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FORMULA
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a(n) = C[A001358(n), n].
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EXAMPLE
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a(1) = C[4,1] = 4.
a(2) = C[6,2] = 15.
a(3) = C[9,3] = 84.
a(4) = C[10,4] = 210.
a(5) = C[14,5] = 2002.
a(6) = C[15,6] = 5005.
a(7) = C[21,7] = 116280.
a(8) = C[22,8] = 319770.
a(9) = C[25,9] = 2042975.
a(10) = C[26,10] = 5311735.
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CROSSREFS
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Cf. A001358, A060604.
Sequence in context: A068313 A129653 A081722 this_sequence A143340 A130679 A107874
Adjacent sequences: A117924 A117925 A117926 this_sequence A117928 A117929 A117930
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), May 03 2006
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