A122465 a(n) is the smallest number k such that gpf(k-j) <= floor((k-j)^(1/n)) for 0<=j<=3 where gpf(k) is the greatest prime factor of k.

5, 1521, 3678726, 22377473783

Offset

1,1

Comments

These were found by Robert Gerbicz.

These numbers could be called "smooth power quartets".

Links

Table of n, a(n) for n=1..4.

Fred Schneider and R. Gerbicz, Smooth Power Trios.

Example

For n=2: 1521 = 3^2*13^2, 13 <= floor(sqrt(1521)) = 39; 1520 = 2^4*5*19 <= 38; 1519 = 7^2*31, 31 <= 38; 1518 = 2*3*11*23, 23 <= 38; and no number smaller than 1521 has this property.

Crossrefs

Cf. A122463, A122464.

Sequence in context: A169620 A181992 A145694 * A184970 A184973 A184971

Adjacent sequences: A122462 A122463 A122464 * A122466 A122467 A122468

Keyword

hard,more,nonn

Author

Fred Schneider, Sep 09 2006

Extensions

a(2) corrected and entry edited by Sean A. Irvine, Mar 28 2026

Status

approved