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A070073
Number of distinct cuboids with integer sides <= n and cubefree volume.
2
1, 3, 8, 11, 23, 33, 57, 57, 70, 95, 142, 156, 220, 271, 338, 338, 441, 480, 609, 658, 775, 896, 1090, 1090, 1220, 1387, 1387, 1468, 1737, 1882, 2197, 2197, 2474, 2735, 3078, 3153, 3592, 3923, 4328, 4328, 4861, 5195, 5794
OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Cubefree.
EXAMPLE
There are eleven cuboids with sides <= 4 having a cubefree volume: 1 X 1 X 1, 1 X 1 X 2, 1 X 1 X 3, 1 X 1 X 4, 1 X 2 X 2, 1 X 2 X 3, 1 X 3 X 3, 1 X 3 X 4, 2 X 2 X 3, 2 X 3 X 3 and 3 X 3 X 4 whereas 1 X 2 X 4, 1 X 4 X 4, 2 X 2 X 2, 2 X 2 X 4, 2 X 3 X 4, 2 X 4 X 4, 3 X 3 X 3 and 4 X 4 X 4 are not cubefree; therefore a(4)=11.
PROG
(Haskell)
a070073 n = length [() | x <- [1..n], y <- [1..x], z <- [1..y],
a212793 (x*y*z) == 1]
-- Reinhard Zumkeller, May 27 2012
CROSSREFS
Cf. A212793.
Sequence in context: A171672 A341262 A361992 * A334539 A058565 A170901
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 21 2002
STATUS
approved