A330900 Number of terms of A066038 that do not exceed 10^n.

0, 2, 22, 130, 1196, 11698, 107315, 961924, 8641491, 78304633, 714962670, 6572968299

Offset

0,2

Comments

Luca & Moodley (2020) conjectured that a(n) ~ exp(gamma) * A006880(n).

Links

Table of n, a(n) for n=0..11.

Florian Luca and Damon Moodley, Composite positive integers whose sum of prime factors is prime, Archivum Mathematicum, Vol. 56, No. 1 (2020), pp. 49-64.

Example

There are 2 terms of A066038 not exceeding 10^1: 6 and 10. Thus a(1) = 2.

Mathematica

b[1] = 0; b[n_] := Plus @@ FactorInteger[n][[;; , 1]]; bQ[n_] := PrimeNu[n] > 1 && PrimeQ[b[n]]; p = 1; s = 0; seq = {}; Do[If[bQ[n], s++]; If[n == p, p *= 10; AppendTo[seq, s]], {n, 1, 10^6}]; seq

Crossrefs

Cf. A006880, A008472, A066038, A073004.

Sequence in context: A292732 A206418 A255866 * A356341 A353191 A062180

Adjacent sequences: A330897 A330898 A330899 * A330901 A330902 A330903

Keyword

nonn,more

Author

Amiram Eldar, May 01 2020

Extensions

a(11) from Giovanni Resta, May 05 2020

Status

approved