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A186525 Semiprimes of the form 7k+1. 1
15, 22, 57, 85, 106, 134, 141, 155, 169, 183, 218, 253, 267, 274, 295, 302, 309, 323, 358, 365, 386, 393, 407, 505, 519, 526, 533, 554, 589, 687, 694, 771, 778, 785, 799, 813, 841, 862, 869, 939, 974, 995, 1037, 1079, 1114, 1121, 1135, 1142, 1149, 1177, 1191 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
15=3*5=1+2*7, 22=2*11=1+3*7.
MATHEMATICA
semiPrimeQ[n_] := Total[FactorInteger[n]][[2]] == 2; Select[7*Range[150] + 1, semiPrimeQ] (* Alonso del Arte, Feb 23 2011 *)
PROG
(PARI) forstep(n=1, 1000, 7, bigomega(n)==2&print1(n", "))
(Magma) IsSemiprime:= func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [1..200] | IsSemiprime(s) where s is 7*n + 1]; // Vincenzo Librandi, Sep 22 2012
CROSSREFS
Cf. A106143 Semiprimes (mod 7).
Sequence in context: A114867 A109288 A018889 * A236107 A065728 A344134
KEYWORD
nonn
AUTHOR
Zak Seidov, Feb 23 2011
STATUS
approved

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)