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A159253 a(n) is the smallest positive integer not yet in the sequence such that n * a(n) is a cube. 2
1, 4, 9, 2, 25, 36, 49, 8, 3, 100, 121, 18, 169, 196, 225, 32, 289, 12, 361, 50, 441, 484, 529, 72, 5, 676, 27, 98, 841, 900, 961, 16, 1089, 1156, 1225, 6, 1369, 1444, 1521, 200, 1681, 1764, 1849, 242, 75, 2116, 2209, 288, 7, 20, 2601, 338, 2809, 108, 3025, 392 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This is a self-inverse permutation of the positive integers.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

Multiplicative with a(p^{3n}) = p^{3n}, a(p^{3n+1}) = p^{3n+2), and a(p^{3n+2)) = p^{3n+1).

MATHEMATICA

f[p_, e_] := If[(r = Mod[e, 3]) == 0, p^e, p^(e - (-1)^r)]; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Aug 29 2019 *)

CROSSREFS

Cf. A064429 (function on exponents)

Sequence in context: A007914 A048758 A277802 * A011262 A073843 A073842

Adjacent sequences:  A159250 A159251 A159252 * A159254 A159255 A159256

KEYWORD

mult,nonn

AUTHOR

Franklin T. Adams-Watters, Apr 07 2009

STATUS

approved

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Last modified December 1 01:37 EST 2021. Contains 349426 sequences. (Running on oeis4.)