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Search: id:A128972
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| A128972 |
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n^3 - 1 divided by its largest cube divisor. |
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+0
2
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| 7, 26, 63, 124, 215, 342, 511, 91, 37, 1330, 1727, 2196, 2743, 3374, 4095, 614, 17, 254, 7999
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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In other words, cubefree part of n^3-1, or cube-free kernel of n^3-1. Cube analogue of A068310.
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FORMULA
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a(n) = A062378(A068601(n)) = A062378(n^3-1).
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EXAMPLE
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a(9) = (9^3-1)/8 = (2^3 * 7 * 13)/(2^3) = 728/8 = 91.
a(10) = (10^3-1)/27 = (3^3 * 37)/(3^3) = 999/27 = 37.
a(18) = (18^3-1)/343 = (7^3 * 17)/(7^3) = 5831/343 = 17.
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CROSSREFS
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Cf. A002350, A004709, A007948, A062378, A067872, A033314, A068310.
Sequence in context: A059376 A049453 A046433 this_sequence A135300 A024001 A068601
Adjacent sequences: A128969 A128970 A128971 this_sequence A128973 A128974 A128975
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Apr 28 2007
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