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A100113 a(n) = n if n <= 2, otherwise (smallest squarefree number m not occurring earlier such that gcd(m, a(n-1)) > 1). 2
1, 2, 6, 3, 15, 5, 10, 14, 7, 21, 30, 22, 11, 33, 39, 13, 26, 34, 17, 51, 42, 35, 55, 65, 70, 38, 19, 57, 66, 46, 23, 69, 78, 58, 29, 87, 93, 31, 62, 74, 37, 111, 102, 82, 41, 123, 105, 77, 91, 119, 85, 95, 110, 86, 43, 129, 114, 94, 47, 141, 138, 106, 53, 159, 165, 115, 130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(A100112(n)) and A100114(A100112(n)) define a pair of inverse permutations of the squarefree numbers: a(A100112(A100114(n))) = A100114(A100112(a(n))) = A005117(n);

A100115(n) = if n is squarefree then a(A100112(n)), otherwise n.

LINKS

Table of n, a(n) for n=1..67.

Eric Weisstein's World of Mathematics, Squarefree

CROSSREFS

Sequence in context: A331441 A209664 A072647 * A300012 A302781 A303760

Adjacent sequences:  A100110 A100111 A100112 * A100114 A100115 A100116

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 07 2004

STATUS

approved

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Last modified October 1 11:59 EDT 2020. Contains 337443 sequences. (Running on oeis4.)