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A115585 Semiprimes with a semiprime sum of factors. 5
4, 9, 14, 21, 25, 26, 33, 38, 46, 49, 57, 62, 69, 74, 85, 93, 94, 106, 121, 129, 133, 134, 145, 166, 169, 177, 178, 205, 213, 217, 218, 226, 237, 249, 253, 254, 262, 265, 278, 289, 309, 314, 334, 361, 362, 393, 398, 417, 422, 445, 466, 469, 489, 493, 502, 505 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

314 = 2*157 and 2 + 157 = 159 =3 * 53 (semiprime).

MATHEMATICA

fQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; Select[ Range@513, fQ@# && fQ[ Plus @@ Flatten[ Table[First@#, {Last@#}] & /@ FactorInteger@# ]] &] (* Robert G. Wilson v *)

Select[Range[600], PrimeOmega[#]==PrimeOmega[Total[Flatten[Table[#[[1]], {#[[2]]}]&/@FactorInteger[#]]]]==2&] (* Harvey P. Dale, Jan 22 2013 *)

PROG

(PARI) list(lim)=my(v=List()); forprime(p=2, sqrt(lim), forprime(q=p, lim\p, if(bigomega(p+q)==2, listput(v, p*q)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Sep 09 2012

CROSSREFS

Cf. A001358, A068318.

Sequence in context: A313154 A313155 A023488 * A099980 A281314 A004630

Adjacent sequences:  A115582 A115583 A115584 * A115586 A115587 A115588

KEYWORD

nonn

AUTHOR

Zak Seidov, Mar 09 2006

EXTENSIONS

More terms from Robert G. Wilson v, Apr 12 2006

STATUS

approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)