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A108633
Nonsquare semiprimes with semiprime sum of factors.
2
14, 21, 26, 33, 38, 46, 57, 62, 69, 74, 85, 93, 94, 106, 129, 133, 134, 145, 166, 177, 178, 205, 213, 217, 218, 226, 237, 249, 253, 254, 262, 265, 278, 309, 314, 334, 362, 393, 398, 417, 422, 445, 466, 469, 489, 493, 502, 505, 514, 517, 526, 553, 565, 573, 586
OFFSET
1,1
COMMENTS
Squares of primes are not included. - Zak Seidov, Sep 14 2018
EXAMPLE
21 = 3*7 and 3 + 7 = 10 = 2*5.
MATHEMATICA
Select[Range[800], Plus@@Last/@FactorInteger[ # ]==Plus@@Last/@FactorInteger[(Plus@@First/@FactorInteger[ # ])]==2&]
PROG
(PARI) is(n) = if(bigomega(n)!=2, return(0), my(f=factor(n)[, 1]~); #f==2 && bigomega(sum(i=1, #f, f[i]))==2) \\ Felix Fröhlich, Sep 17 2018
CROSSREFS
Cf. A001358 (semiprimes), A006881 (squarefree semiprimes).
Sequence in context: A324073 A006614 A039832 * A110478 A125967 A284808
KEYWORD
nonn
AUTHOR
Zak Seidov, Jun 14 2005
EXTENSIONS
Name clarified by David A. Corneth, Sep 17 2018
STATUS
approved