A139224 M(M-1)/2, where M is Mersenne prime A000668(n).

3, 21, 465, 8001, 33542145, 8589737985, 137438167041, 2305843005992468481, 2658455991569831742348849606740148225, 191561942608236107294793377465333618488307184098607105

Offset

1,1

Comments

Perfect number A000396(n) minus Mersenne prime A000668(n).

Links

Table of n, a(n) for n=1..10.

Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos".

Formula

a(n)=A000668(n)*(A000668(n)-1)/2. Also a(n)=A000396(n)-A000668(n).

Crossrefs

Cf. A000217, A000396, A000668, A036689, A139096, A139115, A139116, A139223, A139225, A139226, A139256, A139306.

Sequence in context: A120603 A336578 A285380 * A032469 A006927 A014375

Adjacent sequences: A139221 A139222 A139223 * A139225 A139226 A139227

Keyword

nonn

Author

Omar E. Pol, May 10 2008

Extensions

More terms from Max Alekseyev, Mar 09 2009

Status

approved