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A331019
a(n) is the least k such that the denominator(sigma(sigma(k*n))/(k*n)) equals n.
2
1, 15, 1, 8, 1, 144, 1, 16, 1, 1, 1, 8, 1, 255, 3, 16, 1, 12, 1, 2, 7, 1, 1, 288, 1, 18, 21, 8, 1, 84, 1, 13, 1, 11, 1, 4096, 1, 4, 3, 270, 1, 2448, 1, 2, 3, 1, 1, 16, 1, 420, 3, 1, 1, 124, 3, 16, 3, 128, 1, 616, 1, 85, 3, 16, 1, 1, 1, 8, 3, 1, 1, 32, 1, 64
OFFSET
1,2
COMMENTS
a(n) is the least k such that the A318060(k*n) equals n.
LINKS
FORMULA
a(n) = A331033(n)/n.
PROG
(PARI) a(n) = my(k=n); while (denominator(sigma(sigma(k))/k) != n, k+=n); k/n;
CROSSREFS
Cf. A000203 (sigma), A051027 (sigma(sigma)), A318060.
Sequence in context: A040234 A040235 A040236 * A185903 A040237 A317835
KEYWORD
nonn
AUTHOR
Ray Chandler, Jan 09 2020
STATUS
approved