A389477 Primes p such that psi(p+3) = psi(p+4) = psi(p+5).

11, 41, 59, 953

Offset

1,1

Comments

If it exists, a(5) > 4*10^10.

Links

Table of n, a(n) for n=1..4.

Example

11 is in the sequence since psi(11+3) = psi(11+4) = psi(11+5) = 24.

Mathematica

psi[n_] := psi[k] = n * Times @@ (1 + 1/FactorInteger[n][[;; , 1]]); psi[1] = 1; Select[Prime[Range[200]], psi[#+3] == psi[#+4] == psi[#+5] &] (* Amiram Eldar, Oct 05 2025 *)

Crossrefs

Cf. A000040, A001615, A119711, A387733, A389278.

Sequence in context: A192820 A383296 A078653 * A040167 A040170 A333085

Adjacent sequences: A389474 A389475 A389476 * A389478 A389479 A389480

Keyword

nonn,hard,more

Author

S. I. Dimitrov, Oct 05 2025

Status

approved