OFFSET
1,1
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
JRM Antalan, JAB Dris, Some New Results On Even Almost Perfect Numbers Which Are Not Powers Of Two, arXiv preprint arXiv:1602.04248, 2016
H. J. J. te Riele, Rules for constructing hyperperfect numbers, Fibonacci Quarterly, 22(1)1984, 50-60. See equation (3), the set M*.
EXAMPLE
For x=77, sigma(77)=96, 96-77=19, which divides 77-1.
MATHEMATICA
Select[Range[2, 250], Divisible[#-1, DivisorSigma[1, #]-#]&] (* Harvey P. Dale, Jan 18 2011 *)
PROG
(Magma) [n : n in [2..1000] | (n-1) mod (SumOfDivisors(n)-n) eq 0 ]; /* N. J. A. Sloane, Dec 23 2006 */
(PARI) is(n)=n>1 && (n-1)%(sigma(n)-n)==0 \\ Charles R Greathouse IV, Oct 21 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Jud McCranie, Dec 18 2000
STATUS
approved