This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A020475 a(n) is number of k for which C(n,k) is divisible by n. 9
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS 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 LINKS 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. FORMULA a(n) = n + 1 - A007012(n). - T. D. Noe, Feb 23 2006 MATHEMATICA 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 *) PROG (Haskell) a020475 n = a020475_list !! n a020475_list = 0 : map (sum . map (0 ^)) (tail a053200_tabl) -- Reinhard Zumkeller, Jan 24 2014 CROSSREFS Sequence in context: A277891 A102722 A225530 * A156995 A131183 A133770 Adjacent sequences:  A020472 A020473 A020474 * A020476 A020477 A020478 KEYWORD nonn AUTHOR EXTENSIONS More terms from T. D. Noe, Feb 23 2006 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 16 15:27 EDT 2018. Contains 316264 sequences. (Running on oeis4.)