%I
%S 2,5,8,12,17
%N Maximal number of steps in a nontouching path on an n X n grid such that each step has a different length.
%C a(7) >= 22, see illustration in Links.
%H Giovanni Resta, <a href="/A272719/a272719.png">Illustration of a(2)a(6) and a(7) >= 22</a>
%e An example for a(6)=17:
%e 
%e . 2 5 7 9 15
%e 3 1 . . 11 17
%e . . . . . .
%e . 6 . 12 . .
%e 4 10 . . . .
%e 8 13 . 14 16 18
%Y Cf. A226595.
%K nonn,hard,more
%O 2,1
%A _Giovanni Resta_, May 05 2016
