A068495 Composite n such that n reduced mod(phi(n)) = sigma(n) reduced mod(n).

6, 56, 260, 780, 992, 1976, 2156, 3696, 5520, 13800, 16256, 19872, 22560, 23688, 25232, 41072, 87000, 89964, 133984, 145888, 366720, 785808, 851760, 1100864, 1235052, 1270208, 1439552, 1470720, 2129400, 2237888, 4729664, 8690112

Offset: 1

Author

Benoit Cloitre, Mar 11 2002

Keywords

• easy
• nonn

Comments

Are all terms even? - Robert Israel, Jan 13 2017

Crossrefs

Contains A139256(n) for n > 1.

Programs

Maple

select(n -> not isprime(n) and n mod numtheory:-phi(n) = numtheory:-sigma(n) mod n, [$2..10^7]); # Robert Israel, Jan 13 2017

PARI

for(n=3,500000, if(n%eulerphi(n)==(1-isprime(n))*sigma(n)%n,print1(n,",")))

Extensions

a(31) and a(32) from Robert Israel, Jan 13 2017