A320877 a(n) = 1 + Sum_{k=1..n} 2^prime(k).

1, 5, 13, 45, 173, 2221, 10413, 141485, 665773, 9054381, 545925293, 2693408941, 140132362413, 2339155617965, 11135248640173, 151872736995501, 9159071991736493, 585619824295159981, 2891462833508853933, 150465415423185266861, 2511648656858007873709, 11956381622597298301101

Offset: 0

Author

M. F. Hasler, Oct 30 2018

Keywords

• nonn

Comments

Indices of noncomposite terms are 0, 1, 2, 4, 5, 8, 43, 127, 251, ...

Crossrefs

Cf. A076793.

Programs

Mathematica

Join[{1},Accumulate[2^Prime[Range[30]]]+1] (* Harvey P. Dale, Mar 26 2019 *)

PARI

apply( A320877(n)=1+sum(k=1,n,2^prime(k)), [0..30])

Formula

a(n) = A076793(n) + 1.