2,2

a(8) >= 22, see picture in Links.

Table of n, a(n) for n=2..7.

Giovanni Resta, Illustration of a(3)-a(7) and a(8) >= 22

a(5)=9 because of this polygon on a 5 X 5 grid:

2 . . . .

. . 1 3 5

. . 4 . 7

. 6 . . 8

9 . . . .

See Links for other examples.

Cf. A255981.

Sequence in context: A127621 A049707 A213685 * A261956 A344683 A166633

Adjacent sequences: A271446 A271447 A271448 * A271450 A271451 A271452

nonn,more

Giovanni Resta, May 05 2016

approved