OFFSET
1,1
COMMENTS
Also numbers n such that antisigma(n+1) - antisigma(n-1) = 2*n - 1.
Antisigma(n) = A024816(n) = sum of nondivisors of n.
Union of A014574 (average of twin prime pairs) and sequence 435, 8576, 8826, … (= all terms < 100000).
If n = average of twin prime pairs (q < p) then antisigma(p) - antisigma(q) = 2*n - 1 = p + q - 1.
No term found below 2*10^9 to continue sequence 435, 8576, 8826, ... - Michel Marcus, Mar 19 2013
LINKS
Jaroslav Krizek, Table of n, a(n) for n = 1..1227 (all terms < 100000)
EXAMPLE
Number 435 is in sequence because antisigma(436) - antisigma(434) = 94496 - 93627 = 869 = 2*435 - 1.
MATHEMATICA
Flatten[Position[Partition[DivisorSigma[1, Range[1500]], 3, 1], _?(#[[3]]- #[[1]] == 2&), 1, Heads->False]]+1 (* Harvey P. Dale, May 03 2018 *)
PROG
(PARI) isok(n) = (sigma(n+1) - sigma(n-1)) == 2; \\ Michel Marcus, May 20 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Mar 17 2013
STATUS
approved