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A213734
Primes in A213650.
0
3, 7, 59, 137, 277, 313, 499, 563, 619, 719, 787, 797, 919, 937, 971, 1013, 1217, 1283, 1373, 1409, 1439, 1451, 1621, 1747, 1789, 2207, 2237, 2267, 2393, 2417, 2441, 2591, 2707, 2797, 2801, 2939, 2999, 3251, 3529, 3769, 3847, 4201, 4441, 4447, 4597, 4643, 4721
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
Cf. A213650.
Sequence in context: A320724 A259266 A131652 * A185846 A239023 A341718
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 19 2012
STATUS
approved