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A015870 Numbers k such that phi(k + 4) | sigma(k) + 4. 0
6, 11, 12, 62, 65, 166, 251, 782, 2342, 6662, 25040, 83623931, 933180002, 943169410, 1840122962, 4294967291 (list; graph; refs; listen; history; text; internal format)
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
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
Sequence in context: A212773 A230996 A219553 * A004471 A175021 A315367
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
a(16) from Donovan Johnson, Feb 28 2012
STATUS
approved

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Last modified May 26 08:37 EDT 2024. Contains 372814 sequences. (Running on oeis4.)