A122146 Numbers k such that q(k) = M(k) and 4*q(k) <= k, where q(k) is the largest prime divisor of k and M(k) is the largest prime power divisor of k.

20, 28, 30, 35, 42, 44, 52, 55, 60, 65, 66, 68, 70, 76, 77, 78, 84, 85, 88, 91, 92, 95, 99, 102, 104, 105, 110, 114, 115, 116, 117, 119, 124, 130, 132, 133, 136, 138, 140, 143, 145, 148, 152, 153, 154, 155, 156, 161, 164, 165, 170, 171, 172, 174, 182, 184, 185

Offset: 1

Author

Douglas Stones (dssto1(AT)student.monash.edu.au), Aug 22 2006

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006530, A034699, A122144, A122145.

Programs

Mathematica

Select[Range[200], Max[Power @@@ (f = FactorInteger[#])] == f[[-1, 1]] <= #/4 &] (* Amiram Eldar, May 23 2024 *)

PARI

isok(k) = {my(f = factor(k), pm = 0); if(k > 1 && 4 * f[#f~, 1] <= k, for(i = 1, #f~, pm = max(pm, f[i, 1]^f[i, 2])); pm == f[#f~, 1], 0);} \\ Amiram Eldar, May 23 2024

Extensions

Edited by Ray Chandler, Aug 23 2006