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A139224 M(M-1)/2, where M is Mersenne prime A000668(n). 7
3, 21, 465, 8001, 33542145, 8589737985, 137438167041, 2305843005992468481, 2658455991569831742348849606740148225, 191561942608236107294793377465333618488307184098607105 (list; graph; refs; listen; history; text; internal format)
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: A084620 A120603 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

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Last modified January 23 01:30 EST 2020. Contains 331166 sequences. (Running on oeis4.)