OFFSET
2,3
COMMENTS
This sequence is essentially the same as the number of paths from 1 to n. However, starting from 2 removes the ambiguity of how many maps there are from 1 to 2.
a(2n+1) = a(2n) for all n because x + x^j is odd if and only if x is even and j = 0.
LINKS
Peter Kagey, Table of n, a(n) for n = 2..10000
EXAMPLE
For n = 8 the a(8) = 6 paths are:
2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 with j = [0,0,0,0,0,0]
2 -> 3 -> 4 -> 8 with j = [0,0,1]
2 -> 3 -> 6 -> 7 -> 8 with j = [0,1,0,0]
2 -> 4 -> 5 -> 6 -> 7 -> 8 with j = [1,0,0,0,0]
2 -> 4 -> 8 with j = [1,1]
2 -> 6 -> 7 -> 8 with j = [2,0,0]
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Kagey, Oct 15 2019
STATUS
approved