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A015796
Numbers k such that phi(k) + 5 | sigma(k).
0
4, 10, 32, 60, 88, 688, 2544, 3424, 12200, 62848, 777984, 1037824, 16734208, 67022848, 8625555968, 51537444864, 1099500617728
OFFSET
1,1
COMMENTS
a(18) <= 17592142004224. In general, if 2^k-11 is prime (A096817) then 2^(k-2)*3*(2^k-11) is a term for k > 3. Moreover, if 2^k-21 is prime (A096820) then 2^(k-2)*(2^k-21) is a term for k > 4. - Giovanni Resta, Sep 09 2019
MATHEMATICA
Select[Range[100000],
Divisible[DivisorSigma[1, #], EulerPhi[#] + 5] &] (* David Nacin, Feb 28 2012 *)
KEYWORD
nonn,more
EXTENSIONS
More terms from Jud McCranie, Dec 26 1999
Offset corrected and a(15)-a(16) from Donovan Johnson, Feb 28 2012
a(17) from Giovanni Resta, Sep 09 2019
STATUS
approved