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Search: id:A067391
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| A067391 |
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Least common multiple of numbers in {1,2,3,...,n-1} which do not divide n. |
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+0
2
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| 1, 1, 2, 3, 12, 20, 60, 210, 840, 504, 2520, 27720, 27720, 51480, 360360, 180180, 720720, 4084080, 12252240, 232792560, 232792560, 21162960, 232792560, 5354228880, 5354228880, 2059318800, 26771144400, 80313433200, 80313433200
(list; graph; listen)
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OFFSET
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1,3
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FORMULA
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Let f(n)=lcm(1, 2, ..., n-1)=A003418(n-1). If n=2*p^k for some prime p, then a(n)=f(n)/p; otherwise a(n)=f(n).
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EXAMPLE
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n=10: non-divisors={3,4,6,7,8,9},LCM[3,4,6,7,8,9]=8.9.7=504=a(10)
For n=18, a(n)=lcm(4,5,7,8,10,11,12,13,14,15,16,17)=4084080.
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MATHEMATICA
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a[n_] := LCM@@Select[Range[1, n-1], Mod[n, # ]!=0& ]
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CROSSREFS
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Cf. A049820 [count], A007978 [min], A024816 [sum], A055067 [product].
Cf. A003418, A066574, A038610.
Sequence in context: A130089 A126292 A083265 this_sequence A096361 A105045 A076000
Adjacent sequences: A067388 A067389 A067390 this_sequence A067392 A067393 A067394
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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), Jan 22 2002
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