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A135322 a(n) = GCD(n!, binomial(2n,n)), where binomial(2n,n) = (2n)!/n!^2. 1
1, 1, 2, 2, 2, 12, 12, 24, 90, 20, 4, 168, 28, 1400, 5400, 720, 90, 5940, 23100, 46200, 180180, 17160, 1560, 140400, 11700, 45864, 179928, 13328, 52360, 5969040, 397936, 795872, 3133746, 12345060, 726180, 2863224, 159068, 318136, 1255800, 4958800 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

MATHEMATICA

Table[GCD[n!, Binomial[2n, n]], {n, 0, 60}] (* Stefan Steinerberger, Dec 07 2007 *)

PROG

(PARI) valp(n, p)=my(s); while(n\=p, s+=n); s

a(n)=my(s=1, t); forprime(p=2, n, t=valp(n, p); t=min(t, valp(2*n, p)-2*t); if(t, s*=p^t)); s \\ Charles R Greathouse IV, Oct 09 2016

CROSSREFS

Cf. A000984.

Sequence in context: A121223 A139518 A152662 * A106541 A077945 A077991

Adjacent sequences:  A135319 A135320 A135321 * A135323 A135324 A135325

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 06 2007

EXTENSIONS

More terms from Stefan Steinerberger, Dec 07 2007

STATUS

approved

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Last modified April 19 18:37 EDT 2019. Contains 322290 sequences. (Running on oeis4.)