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Search: id:A113550
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| A113550 |
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a(n) = product of n successive numbers up to n, if n is odd a(n) = n*(n-1)*.. = n!,if n is even a(n) = n(n+1)(n+2)... 'n' terms. |
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+0
3
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| 1, 6, 6, 840, 120, 332640, 5040, 259459200, 362880, 335221286400, 39916800, 647647525324800, 6227020800, 1748648318376960000, 1307674368000, 6288139352883548160000, 355687428096000, 29051203810321992499200000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(2n-1)*a(2n) = (4n-1)!. a(1)*a(2) = 3!, a(3)*a(4) = 7!.
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FORMULA
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a(1) = 1, a(2n-1) = (2n-1)!, a(2n) = (4n-1)!/(2n-1)!.
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EXAMPLE
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a(3) = 3*2*1 = 6, a(4)= 4*5*6*7=840.
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MATHEMATICA
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n = 1; anfunc[n_] := (If [EvenQ[n], {an = n, Do[an = an*(n + i), {i, n - 1}]}, an = n! ]; an) Table[anfunc[n], {n, 1, 30}] - Elizabeth A. Blickley (Elizabeth.Blickley(AT)gmail.com), Mar 10 2006
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CROSSREFS
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Cf. A113549.
Adjacent sequences: A113547 A113548 A113549 this_sequence A113551 A113552 A113553
Sequence in context: A085804 A012125 A123190 this_sequence A011098 A010499 A019734
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KEYWORD
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easy,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 03 2005
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EXTENSIONS
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More terms from Elizabeth A. Blickley (Elizabeth.Blickley(AT)gmail.com), Mar 10 2006
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