A375777 Numbers k such that k - rad(k) - 1 is prime, where rad(k) is A007947(k).

8, 9, 12, 16, 18, 24, 25, 27, 28, 32, 36, 40, 45, 48, 49, 54, 56, 60, 63, 64, 75, 76, 84, 90, 96, 98, 100, 108, 112, 120, 121, 124, 126, 136, 144, 148, 152, 153, 160, 171, 175, 180, 184, 189, 196, 198, 204, 207, 208, 220, 228, 232, 243, 250, 261, 264, 270, 276

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Example

12 is a term, because 12 - rad(12) - 1 = 12 - (2 * 3) - 1 = 12 - 6 - 1 = 5 is prime.

Mathematica

Select[Range[300], PrimeQ[# - Times @@ FactorInteger[#][[;; , 1]] - 1] &] (* Amiram Eldar, Aug 27 2024 *)

Prog

(PARI) isok(k) = isprime(k - (vecprod(factor(k)[, 1])) - 1);

Crossrefs

Cf. A007947, A097379, A359213, A374593.

Sequence in context: A179443 A264828 A080756 * A304661 A189833 A336711

Adjacent sequences: A375774 A375775 A375776 * A375778 A375779 A375780

Keyword

nonn

Author

Arsen Vardanyan, Aug 27 2024

Status

approved