A285038 - OEIS

A285038

a(n) = least k such that k*n belongs to A120383.

1, 1, 2, 1, 6, 1, 4, 1, 2, 3, 30, 1, 6, 2, 2, 1, 28, 1, 8, 3, 4, 15, 18, 1, 6, 3, 2, 1, 30, 1, 330, 1, 10, 14, 12, 1, 12, 4, 2, 3, 78, 2, 28, 15, 2, 9, 30, 1, 4, 3, 28, 3, 16, 1, 6, 1, 8, 15, 476, 1, 18, 165, 4, 1, 6, 5, 152, 7, 6, 6, 60, 1, 84, 6, 2, 2, 60, 1

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OFFSET

1,3

COMMENTS

a(2*k+1) is even for any k > 0.

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

EXAMPLE

5 = prime(3); as 5 is coprime to 3, a(5) must be a multiple of 3; 5*3 = prime(3)*prime(2) does not belong to A120383 as it is not divisible by 2; so a(5) must also be divisible by 2; 5*3*2 belongs to A120383, hence a(5) = 3*2 = 6.

7 = prime(4); as 7 is coprime to 4, a(7) must be a multiple of 4; 7*4 belongs to A120383, hence a(7)=4.

PROG

(PARI) complete(n) = my (c=n); my (f=factor(n)); for (i=1, #f~, c = lcm(c, primepi(f[i, 1]))); return (c)

a(n) = my (m=n); while (1, my (mm=complete(m)); if (m==mm, return (m/n), m=mm))

CROSSREFS

Cf. A120383.

Sequence in context: A304527 A321725 A154744 * A243145 A306695 A242926

Adjacent sequences: A285035 A285036 A285037 * A285039 A285040 A285041

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Apr 08 2017

STATUS

approved