OFFSET
1
COMMENTS
Characteristic function of A248792, numbers n such that sigma(n) - 1 is a prime.
LINKS
FORMULA
MATHEMATICA
Table[If[PrimeQ[DivisorSigma[1, n]-1], 1, 0], {n, 120}] (* Harvey P. Dale, Aug 20 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 07 2017
STATUS
approved