A189072 Semiprimes in A007504 (the sum of first n primes).
10, 58, 77, 129, 381, 501, 791, 1371, 1851, 2127, 2427, 2747, 3831, 4227, 4661, 6081, 6338, 7141, 7418, 9206, 9523, 11599, 12718, 15537, 20059, 20546, 21037, 26369, 27517, 29897, 34915, 36227, 45434, 47721, 48494, 49281, 50887, 51698, 52519, 54169, 57547
Offset: 1
Keywords
Examples
10 = 2*5 = A007504(3), 58 = 2*29 = A007504(7), 77 = 7*11 = A007504(8).
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
PS:= ListTools:-PartialSums(select(isprime, [2,seq(i,i=3..10^4,2)])): select(numtheory:-bigomega = 2, PS); # Robert Israel, Jun 23 2017
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Mathematica
semiPrimeQ[n_Integer] := Total[FactorInteger[n]][[2]] == 2; Select[Accumulate[Prime[Range[100]]], semiPrimeQ] (* T. D. Noe, Apr 20 2011 *) With[{nn=200},Select[Accumulate[Prime[Range[nn]]],PrimeOmega[#]==2&]] (* Harvey P. Dale, Dec 22 2018 *)
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PARI
{a=0;s=[];forprime(p=2,10^4,2==bigomega(a=a+p)&s=concat(s,a));s}
Comments