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!)
A280936 Numbers k such that phi(k) = rad(k) * sopfr(k), where phi(k) is the Euler totient function of k, rad(k) the squarefree kernel of k and sopfr(k) the integer log of k. 0
288, 1225, 4116, 35378, 54450, 1693776, 5969418, 9396618 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

Prime factors of 288 are 2, 2, 2, 2, 2, 3, 3. Then phi(288) = 96, rad(288) = 2 * 3 = 6, sopfr(288) = 2 + 2 + 2 + 2 + 2 + 3 + 3 = 16 and 6 * 16 = 96.

MAPLE

with(numtheory): P:=proc(q) local a, k, n; for n from 1 to q do a:=ifactors(n)[2];

if phi(n)=mul(a[k][1], k=1..nops(a))*add(a[k][1]*a[k][2], k=1..nops(a)) then print(n);

fi; od; end: P(10^9);

CROSSREFS

Cf. A000010, A001414, A007947.

Sequence in context: A281236 A237369 A339469 * A250871 A128392 A296784

Adjacent sequences:  A280933 A280934 A280935 * A280937 A280938 A280939

KEYWORD

nonn,more

AUTHOR

Paolo P. Lava, Jan 11 2017

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 2 02:53 EDT 2021. Contains 346409 sequences. (Running on oeis4.)