A144751 a(1) = 3, a(n + 1) = 1 + a(n) + least odd prime factor of a(n).

3, 7, 15, 19, 39, 43, 87, 91, 99, 103, 207, 211, 423, 427, 435, 439, 879, 883, 1767, 1771, 1779, 1783, 3567, 3571, 7143, 7147, 7155, 7159, 14319, 14323, 28647, 28651, 28659, 28663, 57327, 57331, 114663, 114667, 114675, 114679, 229359

Offset

1,1

Comments

The conjectured g.f. (-4*x^11 + 12*x^10 + 8*x^9 + 24*x^8 + 56*x^7 + 72*x^6 + 43*x^5 + 39*x^4 + 19*x^3 + 15*x^2 + 7*x + 3)/(4*x^12 - 5*x^6 + 1) is wrong; it matches only the first 41 terms of the sequence [R. J. Mathar, Jun 16 2009]

Links

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

Mathematica

vec=NestList[ #+1+Cases[ FactorInteger[ # ][ [ All, 1 ] ], _?OddQ, 1, 1 ][ [ 1 ] ]&, 3, 100 ]
NestList[1+#+Select[FactorInteger[#][[All, 1]], OddQ][[1]]&, 3, 40] (* Harvey P. Dale, Oct 08 2016 *)

Crossrefs

Equals A140525 + 1.

Sequence in context: A186300 A323650 A350696 * A138847 A235699 A077777

Adjacent sequences: A144748 A144749 A144750 * A144752 A144753 A144754

Keyword

nonn

Author

Peter Pein, Feb 09 2009

Status

approved