OFFSET
1,3
LINKS
Jean-François Alcover, Table of n, a(n) for n = 1..46
FORMULA
a(1) = 1, for n >= 2, a(n) = Sum_{k=1..n-1} A000682(k).
EXAMPLE
For n = 5, a(5) = 8:
/\ /\
//\\ /\ / \ /\
///\\\ /\ /\ / \ / /\\ /\ //\\
/\////\\\\, /\//\\//\\, /\/\//\/\\, /\//\//\\\, //\\///\\\,
/\
/\ //\\ starting arch
/\ /\ //\\ /\ ///\\\ (1) (2) (3) (4)
//\\//\\/\, ///\\\//\\, ////\\\\/\, 4 + 2 + 1 + 1 = 8.
MATHEMATICA
a[n_] := If[n == 1, 1, Sum[A000136[[k]]/k, {k, 1, n - 1}]];
a /@ Range[46] (* Jean-François Alcover, Feb 13 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Roger Ford, Dec 07 2019
EXTENSIONS
More terms from Jinyuan Wang, Dec 08 2019
STATUS
approved