A060476 Let n = 2^e_2 * 3^e_3 * 5^e_5 * ... be the prime factorization of n; sequence gives n such that 1 + max{e_2, e_3, ...} is nonprime.

1, 8, 24, 27, 32, 40, 54, 56, 72, 88, 96, 104, 108, 120, 125, 128, 135, 136, 152, 160, 168, 184, 189, 200, 216, 224, 232, 243, 248, 250, 256, 264, 270, 280, 288, 296, 297, 312, 328, 343, 344, 351, 352, 360, 375, 376, 378, 384, 392, 408, 416, 424, 440, 456, 459, 472, 480

Offset

1,2

Comments

The old entry with this sequence number was a duplicate of A005171.

The asymptotic density of this sequence is Sum_{c composite} (1/zeta(c) - 1/zeta(c-1)) = 0.1182437806... - Amiram Eldar, Oct 18 2020

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

From Reinhard Zumkeller, Nov 30 2015: (Start)

A010051(A051903(a(n)+1)) = 1.

a(A055229(n)) > 1 for n > 1. (End)

Mathematica

Join[{1}, Select[Range[500], !PrimeQ[1+Max[FactorInteger[#][[All, 2]]]]&]] (* Jean-François Alcover, Aug 02 2018 *)

Prog

(PARI) isA060476(n) = if(n<2, 1, !isprime(vecmax(factor(n)[, 2])+1))
(Haskell)
a060476 n = a060476_list !! (n-1)
a060476_list = filter ((== 0) . a010051' . (+ 1) . a051903) [1..]
-- Reinhard Zumkeller, Nov 30 2015

Crossrefs

Cf. A096432, A074661.

Cf. A010051, A051903, A055229.

Sequence in context: A375432 A374590 A325990 * A295661 A376142 A240111

Adjacent sequences: A060473 A060474 A060475 * A060477 A060478 A060479

Keyword

nonn

Author

N. J. A. Sloane, Sep 18 2008

Status

approved