OFFSET

1,1

EXAMPLE

a(1)=5 because between s(1)=4 and s(2)=6 there is one prime 5,

a(2)=7 because between s(2)=6 and s(3)=9 there is one prime 7,

a(3)=0 because between s(3)=9 and s(4)=10 there is no primes;

a(4)=24 because between s(4)=10 and s(5)=14 there are two primes 11 and 13 sum of which is 24, (s(n)=n-th semiprime).

MATHEMATICA

With[{sps=Partition[Select[Range[250], PrimeOmega[#]==2&], 2, 1]}, Total[ Select[ Range[ First[#], Last[#]], PrimeQ]]&/@sps] (* Harvey P. Dale, Sep 04 2011 *)

CROSSREFS

KEYWORD

nonn

AUTHOR

Zak Seidov, Dec 22 2007

STATUS

approved