

A287119


Squarefree composite numbers n such that p^2  1 divides n^2  1 for every prime p dividing n.


1



8569, 39689, 321265, 430199, 564719, 585311, 608399, 7056721, 11255201, 17966519, 18996769, 74775791, 75669551, 136209151, 321239359, 446660929, 547674049, 866223359, 1068433631, 1227804929, 1291695119, 2315403649, 2585930689, 7229159729, 7809974369, 8117634239
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OFFSET

1,1


COMMENTS

Such numbers are odd and have at least three prime factors.
Problem: are there infinitely many such numbers?


LINKS

Giovanni Resta, Table of n, a(n) for n = 1..50


PROG

(PARI) isok(n) = {if (issquarefree(n) && !isprime(n), my(f = factor(n)); for (k=1, #f~, if ((n^21) % (f[k, 1]^21), return (0)); ); return (1); ); } \\ Michel Marcus, May 20 2017


CROSSREFS

Cf. A002997, A006972, A175530, A175531.
Subsequence of A120944.
Sequence in context: A217338 A217163 A243839 * A156846 A324711 A221053
Adjacent sequences: A287116 A287117 A287118 * A287120 A287121 A287122


KEYWORD

nonn


AUTHOR

Thomas Ordowski, May 20 2017


EXTENSIONS

More terms from Michel Marcus, May 20 2017
a(14)a(26) from Giovanni Resta, May 20 2017


STATUS

approved



