OFFSET
1,20
COMMENTS
The only negative terms seem to be -1's, occurring as a(1+(2^n)), for n >= 2.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
MATHEMATICA
a[n_] := a[n] = If[n <= 2, 1, a[a[n - 1]] + a[n - a[n - 1]]]; Table[a[#] - a[n - #] &@ a[n - 1] + Boole[n <= 2], {n, 120}] (* Michael De Vlieger, Mar 18 2017, after Robert G. Wilson v at A004001 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Mar 18 2017
STATUS
approved