OFFSET
1,1
COMMENTS
If p < q are primes and a(n) = (p - 1)*(q - 1) + 1, then x^a(n) == x (mod p*q) for every integer x.
LINKS
A. Bogomolny, Euler Function and Theorem
EXAMPLE
181 is a term because 181 = (11 - 1)*(19 - 1) + 1. - Bernard Schott, Jan 19 2019
MATHEMATICA
nmax = 100;
pairs = Table[Table[(Prime[i] - 1)*(Prime[j] - 1) + 1, {i, 1, j - 1}], {j, 2, Prime[nmax]}];
(DeleteDuplicates@Sort@Flatten@pairs)[[1 ;; nmax]]
PROG
(PARI) isok(n) = {if (n % 2, forprime(p = 2, n, forprime(q = p+1, n, if (n == (p - 1)*(q - 1) + 1, return (1)); ); ); ); } \\ Michel Marcus, Feb 25 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Andres Cicuttin, Jan 17 2019
STATUS
approved