A140812 a(n) = A051717(2n) + A051717(2n+1).

3, 9, 60, 84, 60, 132, 5460, 12, 1020, 1596, 660, 276, 5460, 12, 1740, 28644, 1020, 12, 3838380, 12, 27060, 3612, 1380, 564, 92820, 132, 3180, 1596, 1740, 708, 113573460, 12, 1020, 129444, 60, 9372, 280201740, 12, 60, 6636, 460020, 996, 6808620, 12, 122820

Offset

0,1

Comments

All terms are multiples of 3.

Links

G. C. Greubel, Table of n, a(n) for n = 0..2500

Maple

C:=proc(n) if n=0 then RETURN(1); fi; if n mod 2 = 0 then RETURN(bernoulli(n)+bernoulli(n-1)); else RETURN(-bernoulli(n)-bernoulli(n-1)); fi; end:
A051717 := proc(n) denom(C(n)) ; end: A140812 := proc(n) A051717(2*n)+A051717(2*n+1) ; end: seq(A140812(n), n=0..80) ; # R. J. Mathar, Jun 28 2009

Mathematica

A051717 := Join[{1}, Denominator[Total /@ Partition[BernoulliB[Range[0, 500]], 2, 1]]]; Join[{3, 9}, Table[2*A051717[[2*n]], {n, 3, 30}]] (* G. C. Greubel, Dec 22 2017 *)

Crossrefs

Cf. A129826, A140333.

Sequence in context: A261244 A018504 A340389 * A202210 A243425 A018513

Adjacent sequences: A140809 A140810 A140811 * A140813 A140814 A140815

Keyword

nonn

Author

Paul Curtz, Jul 16 2008

Extensions

Edited and extended by R. J. Mathar, Jun 28 2009

Status

approved