A139224 - OEIS

%I #9 Sep 27 2024 05:41:51

%S 3,21,465,8001,33542145,8589737985,137438167041,2305843005992468481,

%T 2658455991569831742348849606740148225,

%U 191561942608236107294793377465333618488307184098607105

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

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

%H Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>.

%F a(n) = A000668(n)*(A000668(n)-1)/2.

%F a(n) = A000396(n)-A000668(n).

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

%K nonn

%O 1,1

%A _Omar E. Pol_, May 10 2008

%E More terms from _Max Alekseyev_, Mar 09 2009