1,1

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

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

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

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

Adjacent sequences: A134869 A134870 A134871 this_sequence A134873 A134874 A134875

Sequence in context: A052395 A034660 A090898 this_sequence A049603 A035527 A085844

nonn

Omar E. Pol (info(AT)polprimos.com), Nov 25 2007