A102750 - OEIS

A102750

Numbers n such that square of largest prime dividing n does not divide n.

2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 17, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 51, 52, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 80, 82, 83, 84, 85

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Numbers n such that the exponent of the largest prime dividing n is one. - Harvey P. Dale, May 02 2019

From Peter Munn, Sep 30 2020: (Start)

2 together with numbers on the left half of the Doudna sequence tree depicted in Antti Karttunen's 2014 comment in A005940.

This sequence and A335738, considered as sets, are related by the self-inverse function A225546(.), which maps the members of either set 1:1 onto the other set.

(End)

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..25000

EXAMPLE

63 is included because 63 = 3^2 *7 and 7 (the largest prime dividing 63) only divides 63 once.

MATHEMATICA

Select[Range[2, 100], FactorInteger[#][[-1, 2]]==1&] (* Harvey P. Dale, May 02 2019 *)

PROG

(PARI) isok(n) = my(f = factor(n)); n % f[#f~, 1]^2; \\ Michel Marcus, May 20 2014

CROSSREFS

Cf. A070003 (complement, apart from the term 1 that is in neither sequence).

Related to A335738 via A225546.