OFFSET
1,1
COMMENTS
In other words, the contiguous substrings of length n are all different if we interpret them as multisets.
Since there are binomial(n+2,2) different triples of nonnegative integers summing up to n, we have the bound a(n) <= binomial(n+2,2)+n-1. Equality holds if and only if n <= 3.
LINKS
EXAMPLE
Maximal strings for n = 1, 2, ..., 8 are:
012
0011220
011122200012
00111122220000121
0100212111000002222211
001011112122220200001012120200
010010220212110100000202222212111110100
021200201101121220202000010111111212222220200
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Nathaniel Johnston, Feb 08 2020
EXTENSIONS
a(9)-a(12) from Bert Dobbelaere, Feb 09 2020
STATUS
approved