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 A128972 n^3 - 1 divided by its largest cube divisor. 2

%I

%S 7,26,63,124,215,342,511,91,37,1330,1727,2196,2743,3374,4095,614,17,

%T 254,7999,9260,10647,12166,13823,1953,17575,19682,813,24388,26999,

%U 29790,32767,4492,39303,42874,46655,1876,54871,59318,63999,8615,74087,79506

%N n^3 - 1 divided by its largest cube divisor.

%C In other words, cubefree part of n^3-1, or cubefree kernel of n^3-1. Cube analog of A068310.

%H Robert Israel, <a href="/A128972/b128972.txt">Table of n, a(n) for n = 2..10000</a>

%F a(n) = A062378(A068601(n)) = A062378(n^3-1).

%e a(9) = (9^3-1)/8 = (2^3 * 7 * 13)/(2^3) = 728/8 = 91.

%e a(10) = (10^3-1)/27 = (3^3 * 37)/(3^3) = 999/27 = 37.

%e a(18) = (18^3-1)/343 = (7^3 * 17)/(7^3) = 5831/343 = 17.

%p a:= n -> mul(f^(f mod 3), f = ifactors(n^3-1)):

%p seq(a(n),n=2..100); # _Robert Israel_, Sep 24 2014

%Y Cf. A002350, A004709, A007948, A062378, A067872, A033314, A068310.

%K easy,nonn

%O 2,1

%A _Jonathan Vos Post_, Apr 28 2007

%E More terms from _Carl R. White_, Nov 09 2010

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Last modified February 23 04:49 EST 2020. Contains 332159 sequences. (Running on oeis4.)