OFFSET
1,1
COMMENTS
Original definition: Abundance-radius=8, that is Abs[sigma[n]-2n]=8 (either +8 or -8). A045770 from 3rd term complemented by -8 cases.
EXAMPLE
22 is in the sequence since sigma(22) = 1 + 2 + 11 + 22 = 36 = 2*22 - 8.
56 is in the sequence since sigma(56) = 1 + 2 + 4 + 7 + 8 + 14 + 28 + 56 = 120 = 2*56 + 8. - Michael B. Porter, Jul 20 2016
MATHEMATICA
Select[Range[1, 10^6], Abs[DivisorSigma[1, #] - 2 #] == 8 &] (* Vincenzo Librandi, Jul 20 2016 *)
PROG
(PARI) is(n)=abs(sigma(n)-2*n)==8 \\ Use, e.g., select(is, [1..10^5]*2). - M. F. Hasler, Jul 19 2016
(Magma) [n: n in [1..2*10^7] | Abs(DivisorSigma(1, n) - 2*n) eq 8]; // Vincenzo Librandi, Jul 20 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 20 2003
EXTENSIONS
More terms from David Wasserman, Aug 18 2005
Edited by M. F. Hasler, Jul 19 2016
STATUS
approved