OFFSET
0,2
COMMENTS
See A290637.
REFERENCES
See A290637.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..12
EXAMPLE
f(3): 1*4*6*7/(2*3*5*8) = 7/10, hence a(3)=10.
MAPLE
g:= (i, j)-> `if`(j=0, i, g(i, j-1)/g(i+2^(j-1), j-1)):
a:= n-> denom(g(1, n)):
seq(a(n), n=0..10); # Alois P. Heinz, Aug 08 2017
MATHEMATICA
f[1] = id[1]/id[2]; f[n_] := f[n] = f[n-1]/(f[n-1] /. id[k_] :> id[k+2^(n-1)]); a[n_]:= f[n] /. id -> Identity//Denominator; Array[a, 8]
PROG
(Python)
from sympy.core.cache import cacheit
from sympy import denom, Rational
@cacheit
def g(i, j): return Rational(i) if j==0 else g(i, j - 1)/g(i + 2**(j - 1), j - 1)
def a(n): return denom(g(1, n))
print([a(n) for n in range(12)]) # Indranil Ghosh, Aug 09 2017, after Maple code
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Jean-François Alcover, Aug 08 2017
STATUS
approved