OFFSET
1,1
COMMENTS
Primes p such that the sum of the first p primes is semiprime.
EXAMPLE
7 is in the sequence because the sum of the first 7 primes is 2 + 3 + 5 + 7 + 11 + 13 + 17 = 58 = 2*29, which is semiprime.
MAPLE
with(numtheory): for n from 1 to 10000 do:s:=sum(‘ithprime(k)’, ’k’=1..n):if bigomega(s)=2 and type(n, prime)=true then printf(`%d, `, n):else fi:od:
MATHEMATICA
Select[Flatten[Position[If[PrimeOmega[#]==2, 1, 0]&/@Accumulate[ Prime[ Range[ 5000]]], 1]], PrimeQ] (* Harvey P. Dale, Jan 27 2022 *)
PROG
(PARI) isok(n) = isprime(n) && bigomega(vecsum(primes(n))) == 2; \\ Michel Marcus, Sep 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 19 2012
STATUS
approved