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Search: id:A076921
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| A076921 |
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Smallest number such that the highest common factor of pair of successive terms follows the pattern 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, ... i.e. b(2n-1)=b(2n)= n given by A004526. |
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+0
1
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| 1, 1, 2, 4, 6, 9, 12, 16, 20, 25, 30, 36, 42, 49, 56, 64, 72, 81, 90, 100, 110, 121, 132, 144, 156, 169, 182, 196, 210, 225, 240, 256, 272, 289, 306, 324, 342, 361, 380, 400, 420, 441, 462, 484, 506, 529, 552, 576, 600, 625, 650, 676, 702, 729, 756, 784
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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(1) a(2n) = n^2, a(2n-1) = n(n+1) = twice the n-th triangular number. (2) Geometric mean of the successive squares interleaved between them.
Essentially the same as A002620.
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CROSSREFS
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Cf. A004526.
Sequence in context: A086378 A088900 A083392 this_sequence A002620 A087811 A025699
Adjacent sequences: A076918 A076919 A076920 this_sequence A076922 A076923 A076924
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 17 2002
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EXTENSIONS
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More terms from Philippe DELEHAM, Jun 20 2005
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