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Search: id:A056042
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| A056042 |
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a(n)=n!/(k!)^2, where k is the largest number such that k! divides n!. |
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+0
3
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| 1, 2, 6, 6, 30, 20, 140, 70, 630, 7, 77, 924, 12012, 3432, 51480, 12870, 218790, 48620, 923780, 184756, 3879876, 705432, 16224936, 2704156, 67603900, 10400600, 280816200, 178296, 5170584, 155117520, 4808643120, 601080390, 19835652870
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OFFSET
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1,2
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COMMENT
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Least integer of the form n!/{(n-k)!}^2.
Similar to but different from A001405.
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EXAMPLE
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E.g. for n=9, 10, 11, 12, a(n)=630, 7, 77, 924 while the corresponding central binomial coefficients are 126, 252, 462, 924 respectively.
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MATHEMATICA
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f[n_] := Min[ Select[ Table[ n!/(n - k)!^2, {k, n}], IntegerQ[ # ] &]]; Table[ f[n], {n, 33}] (Robert G. Wilson v)
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CROSSREFS
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Cf. A000142, A001405, A000188, A055772, A056040.
Cf. A096123, A096125.
Sequence in context: A163641 A070889 A072744 this_sequence A056040 A099566 A147299
Adjacent sequences: A056039 A056040 A056041 this_sequence A056043 A056044 A056045
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jul 25 2000
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