A370881 Numbers k >= 1 such that k = A008472(k)*A066328(k).

2, 60, 84, 231

Offset: 1

Author

Ctibor O. Zizka, Mar 04 2024

Keywords

• nonn
• hard
• more

Comments

a(5) > 10^7, if it exists. - Amiram Eldar, Jul 05 2025

Examples

			k = 60: A008472(60)*A066328(60) = 10*6 = 60 thus k = 60 is a term.
		

Crossrefs

Cf. A008472, A066328.

Programs

Mathematica

q[n_] := n == Times @@ Total[{#, PrimePi[#]} & /@ FactorInteger[n][[;; , 1]]]; Select[Range[250], q] (* Amiram Eldar, Jul 05 2025 *)

PARI

isok(k) = my(p = factor(k)[, 1]); vecsum(p) * vecsum(apply(x -> primepi(x), p)) == k; \\ Amiram Eldar, Jul 05 2025