OFFSET
1,1
COMMENTS
a(1)= 6, the first perfect number. a(2)= 28, the second perfect number. a(3)=248, the dimensions of E_8.
FORMULA
a(n)=A000668(n) * 2^n.
EXAMPLE
a(3)=248 because the third Mersenne prime is 31, 2^3=8 and 31*8=248.
MATHEMATICA
Table[(2^MersennePrimeExponent[n]-1)2^n, {n, 12}] (* Harvey P. Dale, Mar 26 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Nov 25 2007
EXTENSIONS
Spelling corrected and n(7) added by Jason G. Wurtzel, Aug 22 2010
More terms from Harvey P. Dale, Mar 26 2023
STATUS
approved