A068567 Numbers k such that gpf(k) < k/gpf(k) and gpf(k/gpf(k)) < gpf(k), where gpf(n) is the greatest prime factor of n, A006530.

12, 24, 30, 40, 45, 48, 56, 60, 63, 70, 80, 84, 90, 96, 105, 112, 120, 126, 132, 135, 140, 154, 160, 165, 168, 175, 176, 180, 182, 189, 192, 195, 198, 208, 210, 220, 224, 231, 234, 240, 252, 260, 264, 270, 273, 275, 280, 286

Offset

1,1

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Prog

(PARI) gpf(j)={if(j==1, 1, my(f=factor(j)); f[#f[, 2], 1])};
for(k=1, 300, my(L=gpf(k)); if(L<k/L, if(gpf(k/L)<L, print1(k, ", ")))) \\ Hugo Pfoertner, Apr 11 2020

Crossrefs

Cf. A063539.

Sequence in context: A369182 A108938 A085236 * A316099 A082801 A328587

Adjacent sequences: A068564 A068565 A068566 * A068568 A068569 A068570

Keyword

nonn

Author

Reinhard Zumkeller, Mar 25 2002

Status

approved