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A285038 a(n) = least k such that k*n belongs to A120383. 1

%I

%S 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,

%T 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,

%U 1,18,165,4,1,6,5,152,7,6,6,60,1,84,6,2,2,60,1

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

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

%H Rémy Sigrist, <a href="/A285038/b285038.txt">Table of n, a(n) for n = 1..10000</a>

%e 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.

%e 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.

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

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

%Y Cf. A120383.

%K nonn

%O 1,3

%A _Rémy Sigrist_, Apr 08 2017

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Last modified January 17 20:36 EST 2020. Contains 330987 sequences. (Running on oeis4.)