A066909 (product of primes < n that do not divide n) (mod n).

0, 1, 2, 3, 1, 5, 2, 1, 7, 1, 1, 1, 9, 3, 7, 7, 8, 17, 18, 9, 16, 15, 15, 1, 24, 1, 26, 13, 17, 1, 19, 9, 14, 23, 3, 23, 11, 31, 19, 1, 6, 37, 26, 21, 7, 45, 35, 35, 25, 41, 2, 17, 27, 1, 31, 43, 50, 41, 15, 49, 55, 9, 10, 51, 28, 37, 30, 13, 26, 47, 24, 13, 28, 27, 73, 73, 76, 43, 4

Offset: 1

Author

Leroy Quet, Jan 22 2002

Keywords

• nonn
• easy

Examples

			a(8) = (3 * 5 * 7) (mod 8) = 1 because 3, 5 and 7 are the primes < 8 that do not divide 8.
		

Links

• John Tyler Rascoe, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A062347, A066838.

Programs

PARI

a(n) = prod(i=1, n-1, if (isprime(i) && (n%i) , i, 1)) % n; \\ Michel Marcus, May 20 2014

Formula

a(n) = A066838(n) modulo n. - Michel Marcus, May 20 2014

a(prime(n)) = A062347(n-1). - Michel Marcus, May 20 2014