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A136327 Numbers n such that C(2n-1,n-1) mod n == 1. 2
2, 3, 5, 7, 9, 11, 13, 17, 19, 23, 25, 29, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 121, 125, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n such that A099905(n) = 1.

Contains primes, squares of odd primes and cubes of primes >= 5.

See A228562 for terms that are neither primes nor prime powers. [Joerg Arndt, Aug 27 2013]

LINKS

Table of n, a(n) for n=1..60.

McIntosh, R. J. (1995), On the converse of Wolstenholme's theorem, Acta Arithm., LXXI.4 (1995), 381-389.

EXAMPLE

a(3) = 5 because C(9, 4) = 126 == 1 mod 5.

MATHEMATICA

Select[Range[300], Mod[Binomial[2# - 1, # - 1], #] == 1 &] (* Alonso del Arte, May 11 2014 *)

PROG

(PARI) isok(n) = (binomial(2*n-1, n-1) % n) == 1; \\ Michel Marcus, Aug 26 2013

CROSSREFS

Cf. A099905.

Sequence in context: A325395 A070566 A325623 * A095415 A326149 A301987

Adjacent sequences:  A136324 A136325 A136326 * A136328 A136329 A136330

KEYWORD

nonn

AUTHOR

Franz Vrabec, Mar 26 2008

STATUS

approved

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Last modified January 20 14:02 EST 2020. Contains 331094 sequences. (Running on oeis4.)