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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
OFFSET
1,1
COMMENTS
Perfect number A000396(n) minus Mersenne prime A000668(n).
FORMULA
a(n) = A000668(n)*(A000668(n)-1)/2.
a(n) = A000396(n)-A000668(n).
KEYWORD
nonn
AUTHOR
Omar E. Pol, May 10 2008
EXTENSIONS
More terms from Max Alekseyev, Mar 09 2009
STATUS
approved