OFFSET
1,1
COMMENTS
For n > 2, 6 <= a(n) <= n*(n+3)/2. The upper bound occurs for n = 1, 45, 165, 525, 672, 1152, and no others up to 10^9. (Probably this occurs only finitely many times.) - Charles R Greathouse IV, Nov 23 2016
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 21 2016
STATUS
approved