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1, 1, 1, 4, 1, 6, 1, 8, 9, 10, 1, 12, 1, 14, 15, 16, 1, 18, 1, 20, 21, 22, 1, 24, 25, 26, 27, 28, 1, 30, 1, 32, 33, 34, 35, 36, 1, 38, 39, 40, 1, 42, 1, 44, 45, 46, 1, 48, 49, 50, 51, 52, 1, 54, 55, 56, 57, 58, 1, 60, 1, 62, 63
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refs;
listen;
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internal format)
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OFFSET
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1,4
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COMMENTS
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Previous name was: a(n) = 1 if n is a prime number, otherwise, a(n) = n.
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REFERENCES
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Paulo Ribenboim, The little book of big primes, Springer 1991, p. 106.
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LINKS
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FORMULA
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MAPLE
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seq(denom((1 + (n-1)!)/n), n=1..80); # G. C. Greubel, Nov 22 2022
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MATHEMATICA
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a[n_] := ((n-1)! + 1)/n - Floor[(n-1)!/n] // Denominator; Table[a[n] , {n, 1, 63}] (* Jean-François Alcover, Jul 17 2013, after Minac's formula *)
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PROG
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(Magma) [IsPrime(n) select 1 else n: n in [1..70]]; // Vincenzo Librandi, Feb 22 2013
(Sage)
if n == 4: return n
f = factorial(n-1)
return 1/((f + 1)/n - f//n)
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CROSSREFS
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KEYWORD
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dead
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AUTHOR
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STATUS
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approved
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