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A014973 a(n) = n/gcd(n,(n-1)!). 9
1, 2, 3, 2, 5, 1, 7, 1, 1, 1, 11, 1, 13, 1, 1, 1, 17, 1, 19, 1, 1, 1, 23, 1, 1, 1, 1, 1, 29, 1, 31, 1, 1, 1, 1, 1, 37, 1, 1, 1, 41, 1, 43, 1, 1, 1, 47, 1, 1, 1, 1, 1, 53, 1, 1, 1, 1, 1, 59, 1, 61, 1, 1, 1, 1, 1, 67, 1, 1, 1, 71, 1, 73, 1, 1, 1, 1, 1, 79, 1, 1, 1, 83, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Denominator in n!/n^2. Also denominator in Taylor series expansion of dilog function (also called Li_2). - Ralf Stephan, Mar 28 2004

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

FORMULA

a(4) = 2; otherwise a(n) = 1 unless n is a prime in which case a(n) = n. - Ola Veshta (olaveshta(AT)my-deja.com), May 30 2001

a(n) = denominator((i-1)! * Sum_{i=1..n} (1 - 1/i). - Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 16 2004

MATHEMATICA

Table[n/GCD[n, (n-1)!], {n, 90}] (* Harvey P. Dale, Mar 16 2012 *)

Table[Denominator[n!/n^2], {n, 1, 100}] (* Vincenzo Librandi, Apr 15 2014 *)

PROG

(MAGMA) [Denominator(Factorial(n)/n^2): n in [1..80]]; // Vincenzo Librandi, Apr 15 2014

(PARI) a(n)=numerator(polcoeff((x+1)*exp(x+x*O(x^(n-1))), n-1)); \\ Gerry Martens, Aug 12 2015

CROSSREFS

Cf. A092043 (numerators).

Sequence in context: A092509 A214053 A214056 * A276835 A020500 A014963

Adjacent sequences:  A014970 A014971 A014972 * A014974 A014975 A014976

KEYWORD

nonn,easy,frac

AUTHOR

Marc LeBrun

STATUS

approved

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Last modified April 10 02:39 EDT 2020. Contains 333392 sequences. (Running on oeis4.)