A015870 Numbers k such that phi(k + 4) | sigma(k) + 4.

6, 11, 12, 62, 65, 166, 251, 782, 2342, 6662, 25040, 83623931, 933180002, 943169410, 1840122962, 4294967291

Offset

1,1

Comments

There are no other terms < 4290000000. - Jud McCranie, Dec 26 1999

a(17) > 10^12. - Donovan Johnson, Feb 28 2012

Links

Table of n, a(n) for n=1..16.

Example

phi(6+4)=4, which divides 16=sigma(6)+4, so 6 is a term of the sequence.

Mathematica

Select[Range[100000],
Divisible[DivisorSigma[1, #] + 4, EulerPhi[# + 4]] &] (* David Nacin, Feb 28 2012 *)

Prog

(PARI) is(n)=(sigma(n)+4)%eulerphi(n+4)==0 \\ Charles R Greathouse IV, Jan 29 2016

Crossrefs

Cf. A000010, A000203.

Sequence in context: A380509 A230996 A219553 * A004471 A175021 A315367

Adjacent sequences: A015867 A015868 A015869 * A015871 A015872 A015873

Keyword

nonn,more

Author

Robert G. Wilson v

Extensions

a(16) from Donovan Johnson, Feb 28 2012

Status

approved