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A071965 Numbers k such that k = Gpf(k) * Gpf(sigma(k)) where Gpf(k) = A006530(k) is the greatest prime factor of k. 1
15, 33, 51, 69, 91, 95, 141, 145, 159, 213, 287, 295, 321, 395, 445, 473, 573, 581, 679, 703, 745, 895, 973, 995, 1139, 1149, 1169, 1195, 1199, 1293, 1339, 1345, 1441, 1561, 1717, 1757, 1795, 1891, 1941, 2051, 2147, 2167, 2245, 2353, 2395, 2443, 2495, 2589 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[2, 3000], FactorInteger[#][[-1, 1]]FactorInteger[ DivisorSigma[ 1, #]] [[-1, 1]]==#&] (* Harvey P. Dale, Sep 15 2011 *)
PROG
(PARI) for(n=1, 3000, if(vecmax(component(factor(n), 1))*vecmax(component(factor(sigma(n)), 1))==n, print1(n, ", ")))
CROSSREFS
Sequence in context: A190754 A357934 A327900 * A242677 A020184 A231371
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Jun 16 2002
STATUS
approved

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Last modified March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)