login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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. 2
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 9 05:12 EDT 2020. Contains 336319 sequences. (Running on oeis4.)