A389267 a(1) = 2; thereafter a(n) = a(n-1) + b(a(n-1)), where b(k) is the second greatest distinct prime factor of k, or the greatest if there is only one distinct prime factor.

2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 33, 36, 38, 40, 42, 45, 48, 50, 52, 54, 56, 58, 60, 63, 66, 69, 72, 74, 76, 78, 81, 84, 87, 90, 93, 96, 98, 100, 102, 105, 110, 115, 120, 123, 126, 129, 132, 135, 138, 141, 144, 146, 148, 150, 153, 156, 159, 162, 164, 166

Offset

1,1

Links

Xander Lee Luo, Table of n, a(n) for n = 1..10000

Mathematica

s={2}; Do[AppendTo[s, s[[-1]]+If[Length[FactorInteger[s[[-1]]]]==1, FactorInteger[s[[-1]]][[-1, 1]], FactorInteger[s[[-1]]][[-2, 1]]]], {i, 64}]; s (* James C. McMahon, Oct 15 2025 *)

Crossrefs

Cf. A006530, A076820.

Cf. A076271.

Sequence in context: A368861 A141098 A084563 * A194396 A321193 A284788

Adjacent sequences: A389264 A389265 A389266 * A389268 A389269 A389270

Keyword

nonn

Author

Xander Lee Luo, Sep 27 2025

Status

approved