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A020475
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a(n) is number of k for which C(n,k) is divisible by n.
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9
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0, 2, 1, 2, 2, 4, 2, 6, 4, 6, 6, 10, 5, 12, 6, 8, 8, 16, 10, 18, 10, 14, 14, 22, 10, 20, 18, 18, 14, 28, 11, 30, 16, 26, 30, 26, 22, 36, 30, 30, 22, 40, 20, 42, 26, 26, 30, 46, 20, 42, 34, 32, 34, 52, 26, 46, 33, 50, 42, 58, 26, 60, 30, 46, 32, 50, 48, 66, 58, 50, 44, 70, 40, 72, 66, 46, 58
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OFFSET
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0,2
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COMMENTS
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Note that n is prime iff a(n) = n-1. - T. D. Noe, Feb 23 2006
a(n) >= phi(n). (cf. Robbins). - Michel Marcus, Oct 31 2012
For n > 0: number of zeros in n-th row of A053200. - Reinhard Zumkeller, Jan 01 2013
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LINKS
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T. D. Noe, Table of n, a(n) for n = 0..1000
H. Harborth, Divisibility of binomial coefficients by their row number, The American Mathematical Monthly, Vol. 84, No. 1 (Jan., 1977), pp. 35-37.
N. Robbins, On the number of binomial coefficients which are divisible by their row number. , Canad. Math. Bull. 25(1982), 363-365.
N. Robbins, On the number of binomial coefficients which are divisible by their row number. II , Canad. Math. Bull. 28(1985), 481-486.
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FORMULA
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a(n) = n + 1 - A007012(n). - T. D. Noe, Feb 23 2006
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MATHEMATICA
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Table[cnt=0; Do[If[Mod[Binomial[n, k], n]==0, cnt++ ], {k, 0, n}]; cnt, {n, 0, 100}] (* T. D. Noe, Feb 23 2006 *)
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CROSSREFS
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Sequence in context: A054541 A102722 A225530 * A131183 A133770 A184199
Adjacent sequences: A020472 A020473 A020474 * A020476 A020477 A020478
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson
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EXTENSIONS
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More terms from T. D. Noe, Feb 23 2006
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STATUS
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approved
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