OFFSET
1,2
COMMENTS
A variation of A050507 with average of the divisors instead of their sum.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..241 (terms below 10^10)
MATHEMATICA
f[n_] := DivisorSigma[1, n]/DivisorSigma[0, n]; aQ[n_] := f[n + 2] - f[n] == 1 && !(PrimeQ[n] && PrimeQ[n + 2]); Select[Range[1000000], aQ]
PROG
(PARI) isok(k) = !(isprime(k) && isprime(k+2)) && (sigma(k+2)/numdiv(k+2) - sigma(k)/numdiv(k) == 1); \\ Michel Marcus, Jan 22 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jan 11 2019
STATUS
approved