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A083746
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a(1) = 1, a(2) = 2; for n>2, a(n) = 3*(n-2)*(n-2)!.
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5
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1, 2, 3, 12, 54, 288, 1800, 12960, 105840, 967680, 9797760, 108864000, 1317254400, 17244057600, 242853811200, 3661488230400, 58845346560000, 1004293914624000, 18140058832896000, 345728180109312000, 6933770723303424000
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OFFSET
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1,2
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COMMENTS
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a(1) = 1, a(2) = 2, define S(k) = sum of all the terms other than a(k) k < n. a(n) = Sum_{k=1..n-1} S(k).
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LINKS
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FORMULA
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a(n) = (n-2)*Sum_{j=1..n-1} a(j).
Sum_{k=1..n} a(k) = A052560(n-1) for n > 1.
a(n) = A052673(n-2) for n > 2. (End)
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EXAMPLE
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a(4) = {a(1) + a(2)} + {a(1) +a(3)} + {a(2) + a(3)} = 12.
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MAPLE
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a := proc(n) option remember: if n=1 then RETURN(1) fi: if n=2 then RETURN(2) fi: 3*(n-2)*(n-2)! end: for n from 1 to 40 do printf(`%d, `, a(n)) od: # James A. Sellers, May 19 2003
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MATHEMATICA
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PROG
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(Magma) [n le 2 select n else 3*(n-2)*Factorial(n-2): n in [1..40]]; // G. C. Greubel, Feb 03 2024
(SageMath) [1, 2]+[3*(n-2)*factorial(n-2) for n in range(3, 41)] // G. C. Greubel, Feb 03 2024
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 06 2003
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EXTENSIONS
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STATUS
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approved
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