A226386 Numbers n such that rad(phi(n)) < phi(rad(n)), where rad(n) is the squarefree kernel of n, and phi is Euler's totient function.

5, 10, 13, 15, 17, 19, 20, 21, 26, 29, 30, 33, 34, 35, 37, 38, 39, 40, 41, 42, 45, 51, 52, 53, 55, 57, 58, 60, 61, 63, 65, 66, 68, 69, 70, 73, 74, 76, 77, 78, 80, 82, 84, 85, 87, 89, 90, 91, 93, 95, 97, 101, 102, 104, 105, 106, 109, 110, 111, 113, 114, 115

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

rad[n_] := Product[fa[n][[i, 1]], {i, Length[fa[n]]}]; fa = FactorInteger; Select[Range[500], rad[EulerPhi[#]] < EulerPhi[rad[#]] &]

Prog

(PARI) rad(n)=my(f=factor(n)[, 1]); prod(i=1, #f, f[i])
is(n)=my(f=factor(n)[, 1], r=prod(i=1, #f, f[i]), ph=prod(i=1, #f, f[i]-1)*n/r); rad(ph)<eulerphi(r) \\ Charles R Greathouse IV, Dec 13 2013

Crossrefs

Cf. A007947, A000010, A226384.

Sequence in context: A241143 A073503 A313378 * A200995 A049197 A324928

Adjacent sequences: A226383 A226384 A226385 * A226387 A226388 A226389

Keyword

nonn

Author

José María Grau Ribas, Jun 05 2013

Status

approved