A389278 Primes p such that psi(p+1) = psi(p+2).

3, 7, 13, 31, 43, 61, 607, 1033, 1483, 4993, 14143, 33997, 36373, 37663, 56923, 71263, 72673, 89017, 102523, 160081, 177283, 289453, 417337, 640231, 652903, 811183, 822391, 1103353, 1642153, 1865827, 2146387, 2151511, 2581927, 2794111, 3143551, 3167473, 3578383, 3769981, 4043623, 4600711, 5007703

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Example

43 is a term because psi(43+1) = psi(43+2) = 72.

Mathematica

psi[n_] := n * Times @@ (1 + 1/FactorInteger[n][[;; , 1]]); psi[1] = 1; Select[Prime[Range[10^4]], Equal @@ psi /@ (# + {1, 2}) &] (* Amiram Eldar, Sep 28 2025 *)

Crossrefs

Cf. A000040, A001615, A291043, A119705, A389277, A389279.

Sequence in context: A256148 A083520 A336801 * A162869 A079018 A342150

Adjacent sequences: A389275 A389276 A389277 * A389279 A389280 A389281

Keyword

nonn

Author

S. I. Dimitrov, Sep 28 2025

Status

approved