A228151 Denominators of r(n) = r(n-1) + r(n-2) + B_(n-2), where B_n is the n-th Bernoulli number A027641(n)/A027642(n).

1, 1, 1, 2, 3, 6, 5, 30, 105, 70, 35, 70, 231, 2310, 143, 30030, 15015, 10010, 85085, 170170, 373065, 25194, 323323, 1939938, 22309287, 14872858, 168245, 74364290, 15935205, 223092870, 1078282205, 588153930, 20056049013, 5142576670, 393255863, 9550499530

Offset

0,4

Comments

r(n): 0, 0, 1, 1/2, 5/3, 13/6, 19/5, 179/30, 1028/105, 1103/70, 893/35,... = A227500(n)/a(n). a(0)=a(1)=1 is a choice.

Links

Table of n, a(n) for n=0..35.

Prog

(PARI) r(n) = if (n<=1, 0, r(n-1) + r(n-2) + bernfrac(n-2));
a(n) = if (n<=1, 1, denominator(r(n))); \\ Michel Marcus, Aug 24 2013
(Magma) t:=40; r:=[n le 2 select 0 else Self(n-1)+Self(n-2)+BernoulliNumber(n-3): n in [1..t]]; [n le 2 select 1 else Denominator(r[n]): n in [1..t]]; // Bruno Berselli, Sep 05 2013

Crossrefs

Cf. A227500: numerators of r(n), where a(n) is named c(n).

Cf. A027641, A027642.

Sequence in context: A124655 A338219 A066838 * A392599 A276087 A341837

Adjacent sequences: A228148 A228149 A228150 * A228152 A228153 A228154

Keyword

nonn,frac

Author

Paul Curtz, Aug 13 2013

Extensions

More terms from Michel Marcus, Aug 24 2013

Status

approved