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A071964
Numbers k such that k = Gpf(k) * Gpf(phi(k)) where Gpf(k) = A006530(k) is the greatest prime factor of k.
0
4, 6, 9, 10, 21, 25, 34, 39, 49, 55, 57, 111, 121, 155, 169, 203, 205, 219, 253, 289, 291, 301, 305, 327, 361, 489, 497, 505, 514, 529, 579, 689, 737, 755, 791, 841, 889, 905, 961, 979, 1027, 1081, 1205, 1255, 1299, 1355, 1369, 1379, 1461, 1477, 1681, 1703
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[1800], FactorInteger[#][[-1, 1]]FactorInteger[EulerPhi[#]][[-1, 1]] == #&] (* Harvey P. Dale, Mar 25 2023 *)
PROG
(PARI) for(n=1, 3000, if(vecmax(component(factor(n), 1))*vecmax(component(factor(eulerphi(n)), 1))==n, print1(n, ", ")))
(PARI) is(k) = if(k > 2, my(f = factor(k)); k == f[#f~, 1] * vecmax(factor(eulerphi(f))[, 1]), 0); \\ Amiram Eldar, Oct 28 2024
CROSSREFS
Cf. A000010 (phi), A006530, A068211.
Sequence in context: A275197 A118778 A108635 * A135257 A118697 A118695
KEYWORD
easy,nonn,changed
AUTHOR
Benoit Cloitre, Jun 16 2002
STATUS
approved