OFFSET
1,1
COMMENTS
Supersequence of A055574 for k=0 (n satisfying sigma(n+1) = sigma(n-1)). For number 5 is k=1. Are there other such number for k=1 or k=-1?
Corresponding values of integers k: 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,....
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..1000
EXAMPLE
Number 5 is in sequence because sigma(6) - sigma(4) = 12 - 7 = 5 = 1 * 5; k=1.
MATHEMATICA
Select[Range[100000], IntegerQ[(DivisorSigma[1, # + 1] - DivisorSigma[1, # - 1])/#] &] (* T. D. Noe, May 02 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, May 01 2013
EXTENSIONS
Extended by T. D. Noe, May 02 2013
STATUS
approved