A071964 Numbers n such that n = Lpf(n)*Lpf(phi(n)) where Lpf(x) = A006530(x) is the largest prime factor of x.

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

Table of n, a(n) for n=1..52.

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, ", ")))

Crossrefs

Sequence in context: A275197 A118778 A108635 * A135257 A118697 A118695

Adjacent sequences: A071961 A071962 A071963 * A071965 A071966 A071967

Keyword

easy,nonn

Author

Benoit Cloitre, Jun 16 2002

Status

approved