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A112098
Denominator of Sum_{i=1..n} 1/C(2*i,i).
2
1, 2, 3, 60, 420, 630, 13860, 32760, 120120, 2042040, 38798760, 923780, 74364290, 212469400, 150965100, 332727080400, 10314539492400, 3438179830800, 24067258815600, 890488576177200, 890488576177200, 1177742955589200, 1569931359800403600, 2354897039700605400
OFFSET
0,2
FORMULA
Sum_{i >= 1} 1/C(2*i, i) = (2*Pi*sqrt(3) + 9)/27.
EXAMPLE
0, 1/2, 2/3, 43/60, 307/420, 463/630, 10201/13860, 24121/32760, 88453/120120, ... -> (2*Pi*sqrt(3) + 9)/27.
MAPLE
BB:=n->add(1/binomial(2*i, i), i=1..n): a:=n->denom(BB(n)): seq(a(n), n=0..23); # Zerinvary Lajos, Mar 28 2007
MATHEMATICA
Denominator@ Table[Sum[1/Binomial[2 i, i], {i, n}], {n, 0, 23}] (* Michael De Vlieger, Mar 09 2016 *)
PROG
(PARI) a(n) = denominator(sum(i=1, n, 1/binomial(2*i, i))); \\ Michel Marcus, Mar 09 2016
CROSSREFS
Cf. A112098.
Sequence in context: A097961 A145556 A124083 * A144545 A085326 A062308
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Nov 30 2005
STATUS
approved