login
A068368
Composite n such that sigma(2n+1)-sigma(n)=n+1.
0
16, 335, 8399, 12599, 16383, 62999, 546359, 743999, 2815199, 3046655, 3592655, 8422679, 25357439, 26356199, 29318279, 75428999, 112039199, 202417343, 226325999, 329611559, 335894159, 452921039
OFFSET
1,1
COMMENTS
Primes satisfying sigma(2p+1)-sigma(p)=p+1 are Sophie Germain primes A005384(n)
PROG
(PARI) for(n=1, 500000000, if((sigma(2*n+1)-sigma(n)==n+1) && (!isprime(n)), print1(n, ", ")))
CROSSREFS
Sequence in context: A223394 A218476 A240344 * A013993 A058722 A318013
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 28 2002
EXTENSIONS
More terms from Rick L. Shepherd, May 08 2002
STATUS
approved