A101628 Denominator of partial sums of a certain series.

1, 35, 210, 30030, 12012, 1293292, 6466460, 743642900, 6692786100, 6016814703900, 12033629407800, 63606326869800, 63606326869800, 784965679900201800, 784965679900201800, 258253708687166392200, 19865669899012799400, 31905469837808435400, 31905469837808435400, 114827785946272559004600

Offset

1,2

Comments

The numerators are given in A101627.

Links

Table of n, a(n) for n=1..20.

Formula

a(n)=denominator(s(n)) with s(n)=8*sum(1/((3*k-1)*k*(3*k+1)), k=1..n).

Mathematica

Denominator[Accumulate[Table[8/(9k^3-k), {k, 20}]]] (* Harvey P. Dale, Jul 17 2014 *)

Prog

(PARI) a(n) = denominator(24*sum(k=1, n, 1/((3*k-1)*(3*k)*(3*k+1)))); \\ Michel Marcus, Mar 01 2022

Crossrefs

Cf. A101627 (numerators).

Sequence in context: A232713 A007329 A345655 * A064013 A240137 A020262

Adjacent sequences: A101625 A101626 A101627 * A101629 A101630 A101631

Keyword

nonn,frac,easy

Author

Wolfdieter Lang, Dec 23 2004

Extensions

More terms from Michel Marcus, Mar 01 2022

Status

approved