A174342 Denominator of ( A164555(n)/A027642(n) + 1/(n+1) ).

1, 1, 2, 4, 6, 6, 6, 8, 90, 10, 6, 12, 210, 14, 30, 16, 30, 18, 42, 20, 770, 22, 6, 24, 13650, 26, 54, 28, 30, 30, 462, 32, 5610, 34, 210, 36, 51870, 38, 26, 40, 330, 42, 42, 44, 2070, 46, 6, 48, 324870, 50, 1122, 52, 30, 54, 43890, 56, 5510, 58, 6, 60, 930930

Offset: 0

Author

Paul Curtz, Mar 16 2010

Keywords

• nonn
• frac

Comments

The sequence A174341(n)/a(n) = 2, 1, 1/2, 1/4, 1/6, 1/6, 1/6, ... becomes 2, -1, 1/2, -1/4, 1/6,.. under inverse binomial transform: an autosequence, where each second term flips the sign.

Links

• OEIS Wiki, Autosequence

Crossrefs

Cf. A174341 (numerators).

Programs

PARI

B(n)=if(n!=1, bernfrac(n), -bernfrac(n));
a(n)=denominator(B(n) + 1/(n + 1));
for(n=0, 60, print1(a(n),", ")) \\ Indranil Ghosh, Jun 19 2017

Python

from sympy import bernoulli, Rational
def B(n):
    return bernoulli(n) if n != 1 else -bernoulli(n)
def a(n):
    return (B(n) + Rational(1, n + 1)).as_numer_denom()[1]
[a(n) for n in range(61)] # Indranil Ghosh, Jun 19 2017