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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Squares of primes are not included. - Zak Seidov, Sep 14 2018

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

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

Adjacent sequences:  A108630 A108631 A108632 * A108634 A108635 A108636

KEYWORD

nonn

AUTHOR

Zak Seidov, Jun 14 2005

EXTENSIONS

Name clarified by David A. Corneth, Sep 17 2018

STATUS

approved

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Last modified October 18 02:23 EDT 2019. Contains 328135 sequences. (Running on oeis4.)