A111878 a(n) = A111877(n+1)/5.

1, 7, 21, 231, 3003, 3003, 51051, 969969, 969969, 22309287, 111546435, 334639305, 9704539845, 300840735195, 300840735195, 300840735195, 11131107202215, 11131107202215, 456375395290815, 19624141997505045, 19624141997505045

Offset

0,2

Links

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

Formula

a(n) = (1/15)*denominator(digamma(n+7/2)/2 + log(2) + euler_gamma/2).

a(n) = denominator(f(n+2)/15), where f(n) = Sum_{j=0..n} 1/(2*j+1).

a(n) = (1/15) * denominator of ( 2*H_{2*n+6) - H_{n+3} ), where H_{n} is the n-th Harmonic number. - G. C. Greubel, Jul 24 2023

Mathematica

With[{H=HarmonicNumber}, Table[Denominator[2*H[2*n+6] -H[n+3]]/15, {n, 0, 40}]] (* G. C. Greubel, Jul 24 2023 *)

Prog

(Magma) H:=HarmonicNumber; [Denominator((2*H(2*n+6) - H(n+3)))/15: n in [0..40]]; // G. C. Greubel, Jul 24 2023
(SageMath) h=harmonic_number; [denominator(2*h(2*n+6, 1) - h(n+3, 1))/15 for n in range(41)] # G. C. Greubel, Jul 24 2023

Crossrefs

Cf. A025547, A111877.

Sequence in context: A183938 A060146 A357673 * A133279 A192734 A220161

Adjacent sequences: A111875 A111876 A111877 * A111879 A111880 A111881

Keyword

easy,nonn

Author

Paul Barry, Aug 19 2005

Status

approved