1,3

Inspired by A258643 but the axes of symmetry are the same as in A262742. The mirror patterns and nonsquare holes are excluded.

Table of n, a(n) for n=1..18.

Kival Ngaokrajang, Illustration of initial terms

Irregular table begins:

n\k 0 1 2 3 4 5 ...

1 1

2 1

3 3 1

4 3 1

5 28 15 11 0 6 3

6 30 16 0 0 3 3

...

Cf. A258643, A262742.

Sequence in context: A262940 A278601 A281038 * A099906 A262026 A270390

Adjacent sequences: A263674 A263675 A263676 * A263678 A263679 A263680

nonn,tabf,more

Kival Ngaokrajang, Oct 23 2015

approved