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A274546 Numbers n such that 5n is squarefree. 2
1, 2, 3, 6, 7, 11, 13, 14, 17, 19, 21, 22, 23, 26, 29, 31, 33, 34, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 57, 58, 59, 61, 62, 66, 67, 69, 71, 73, 74, 77, 78, 79, 82, 83, 86, 87, 89, 91, 93, 94, 97, 101, 102, 103, 106, 107, 109, 111, 113, 114, 118, 119, 122, 123, 127, 129, 131, 133, 134 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Squarefree numbers coprime to 5.

LINKS

Table of n, a(n) for n=1..69.

FORMULA

a(n) ~ 5n/Pi^2. - Charles R Greathouse IV, Sep 06 2016

EXAMPLE

6 is in this sequence because 5*6 = 30 = 2*3*5 is squarefree.

PROG

(MAGMA) [n: n in [1..135] | IsSquarefree(5*n)];

(PARI) lista(nn) = for(n=1, nn, if(issquarefree(5*n), print1(n, ", "))); \\ Altug Alkan, Sep 05 2016

(PARI) is(n)=n%5 && issquarefree(n) \\ Charles R Greathouse IV, Sep 06 2016

CROSSREFS

Numbers n such that n*A005117(k) is squarefree: A005117 (k = 1), A056911 (k = 2), A261034 (k = 3), this sequence (k = 4), A276378 (k = 6).

Cf. A008587.

Sequence in context: A075995 A102432 A024561 * A113545 A056825 A070757

Adjacent sequences:  A274543 A274544 A274545 * A274547 A274548 A274549

KEYWORD

nonn,easy

AUTHOR

Juri-Stepan Gerasimov, Sep 05 2016

STATUS

approved

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Last modified January 21 19:33 EST 2021. Contains 340352 sequences. (Running on oeis4.)