A033872 Numbers k such that A033831(k) is prime.

8, 10, 12, 14, 15, 16, 18, 20, 21, 22, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 50, 51, 52, 55, 56, 57, 58, 62, 63, 64, 65, 68, 69, 72, 74, 75, 76, 77, 80, 81, 82, 85, 86, 87, 90, 91, 92, 93, 94, 95, 98, 99

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

f[n_] := DivisorSum[n, 1&, # > 2 && n/# < #-1 &]; Select[Range[1000], PrimeQ[f[#]] &] (* Amiram Eldar, Jun 11 2019 *)

Prog

(PARI) isok(n) = isprime(sumdiv(n, d, (d>=3) && (q=n/d) && (q>=1) && (q<=d-2))); \\ Michel Marcus, Jun 11 2019

Crossrefs

Cf. A033831.

Sequence in context: A336143 A347267 A220571 * A080752 A262159 A020744

Adjacent sequences: A033869 A033870 A033871 * A033873 A033874 A033875

Keyword

easy,nonn

Author

Naohiro Nomoto

Status

approved