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A120306 Numerator of the sum of all matrix elements of n X n matrix M[i,j]=CatalanNumber[i]/CatalanNumber[j], where CatalanNumber[k]=(2k)!/k!/(k+1)!=A000108[k]. 0
1, 9, 68, 1364, 12064, 58303, 4517375, 1142991, 4251679307, 138473652271, 240881487689, 857560784067, 49571162119157, 12805922830496929, 167798784068528807, 365691567246838709, 46160923354240494523 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

p divides a(p-1) for primes p in A007645.

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a(n) = Numerator[Sum[Sum[(2i)!/(i!)^2/(i+1)/((2j)!/(j!)^2/(j+1)),{i,1,n}],{j,1,n}]].

MATHEMATICA

Numerator[Table[Sum[Sum[(2i)!/(i!)^2/(i+1)/((2j)!/(j!)^2/(j+1)), {i, 1, n}], {j, 1, n}], {n, 1, 20}]]

CROSSREFS

Cf. A000108, A014138, A007645.

Sequence in context: A121633 A091708 A024119 * A197425 A089379 A193698

Adjacent sequences:  A120303 A120304 A120305 * A120307 A120308 A120309

KEYWORD

frac,nonn

AUTHOR

Alexander Adamchuk, Jul 14 2006

STATUS

approved

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Last modified February 23 15:23 EST 2018. Contains 299581 sequences. (Running on oeis4.)