A320877 - OEIS

%I #8 Mar 26 2019 14:48:54

%S 1,5,13,45,173,2221,10413,141485,665773,9054381,545925293,2693408941,

%T 140132362413,2339155617965,11135248640173,151872736995501,

%U 9159071991736493,585619824295159981,2891462833508853933,150465415423185266861,2511648656858007873709,11956381622597298301101

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

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

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

%t Join[{1},Accumulate[2^Prime[Range[30]]]+1] (* _Harvey P. Dale_, Mar 26 2019 *)

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

%Y Cf. A076793.

%K nonn

%O 0,2

%A _M. F. Hasler_, Oct 30 2018