1,1

a(1)= 6, the first perfect number. a(2)= 28, the second perfect number. a(3)=248, the dimensions of E_8.

Table of n, a(n) for n=1..7.

a(n)=A000668(n) * 2^n.

a(3)=248 because the third Mersenne prime is 31, 2^3=8 and 31*8=248.

Cf. A061029. Powers of 2: A000079. Mersenne primes: A000668.

Sequence in context: A336565 A216413 A090898 * A281003 A049603 A333927

Adjacent sequences: A134869 A134870 A134871 * A134873 A134874 A134875

nonn

Omar E. Pol, Nov 25 2007

Spelling corrected and n(7) added by Jason G. Wurtzel, Aug 22 2010

approved