cp's OEIS Frontend

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.

%I A060476 #20 Oct 18 2020 03:07:51
%S A060476 1,8,24,27,32,40,54,56,72,88,96,104,108,120,125,128,135,136,152,160,
%T A060476 168,184,189,200,216,224,232,243,248,250,256,264,270,280,288,296,297,
%U A060476 312,328,343,344,351,352,360,375,376,378,384,392,408,416,424,440,456,459,472,480
%N 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.
%C A060476 The old entry with this sequence number was a duplicate of A005171.
%C A060476 The asymptotic density of this sequence is Sum_{c composite} (1/zeta(c) - 1/zeta(c-1)) = 0.1182437806... - _Amiram Eldar_, Oct 18 2020
%H A060476 Charles R Greathouse IV, <a href="/A060476/b060476.txt">Table of n, a(n) for n = 1..10000</a>
%F A060476 From _Reinhard Zumkeller_, Nov 30 2015: (Start)
%F A060476 A010051(A051903(a(n)+1)) = 1.
%F A060476 a(A055229(n)) > 1 for n > 1. (End)
%t A060476 Join[{1}, Select[Range[500], !PrimeQ[1+Max[FactorInteger[#][[All, 2]]]]&]] (* _Jean-François Alcover_, Aug 02 2018 *)
%o A060476 (PARI) isA060476(n) = if(n<2,1,!isprime(vecmax(factor(n)[,2])+1))
%o A060476 (Haskell)
%o A060476 a060476 n = a060476_list !! (n-1)
%o A060476 a060476_list = filter ((== 0) . a010051' . (+ 1) . a051903) [1..]
%o A060476 -- _Reinhard Zumkeller_, Nov 30 2015
%Y A060476 Cf. A096432, A074661.
%Y A060476 Cf. A010051, A051903, A055229.
%K A060476 nonn
%O A060476 1,2
%A A060476 _N. J. A. Sloane_, Sep 18 2008