OFFSET
1,3
COMMENTS
a(n) = A046222(n-1) for n > 5. - Georg Fischer, Oct 17 2018
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..3000
EXAMPLE
1/1; 1/1 1/1; 1/1 1/2 1/1; 1/1 3/2 3/2 1/1; 1/1 5/2 3/1 5/2 1/1; 1/1 7/2 11/2 11/2 7/2 1/1; 1/1 9/2 9/1 11/1 9/1 9/2 1/1; 1/1 11/2 27/2 20/1 20/1 27/2 11/2 1/1; ...
MATHEMATICA
Map[{Denominator@ #, Numerator@ #} &@ #[[Ceiling[Length[#]/2] ]] &, Select[Nest[Append[#, Join[{#[[-1, 1]]}, Total /@ Partition[#[[-1]], 2, 1], {#[[-1, -1]]}]] &, {{1}, {1, 1}, {1, 1/2, 1}}, 2 (20) + 1], OddQ@ Length@ # & ]] // Flatten (* or *)
With[{r = Sqrt[1 - 4 x]}, {1, 1, 2, 1}~Join~Riffle[ConstantArray[1, Length@ #], #] &@ CoefficientList[Series[(2 - 2 r - 3 x - r x)/(2 r x^2), {x, 0, 19}], x]] (* Michael De Vlieger, Oct 17 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from James A. Sellers, Dec 13 1999
STATUS
approved