A344301: Minimum number of cells in a nxn grid that need to be painted so that each unpainted cell is orthogonally adjacent to exactly one painted cell. 
Painted cells are shown as 'x', while unpainted cells are '.'
By Dmitry Kamenetsky, 27th May 2021.

a(1)=1
x

a(2)=2
.x
.x

a(3)=3
...
xxx
...

a(4)=4
..x.
x...
...x
.x..

a(5)=8
...xx
xx...
.....
..xxx
x....

a(6)=12
..xx..
x....x
x....x
..xx..
..xx..
x....x

a(7)=15
x....xx
..xx...
.......
xx..xxx
.......
..xx...
x....xx

a(8)=16
...x..x.
xx....x.
....x...
..x....x
x....x..
...x....
.x....xx
.x..x...

a(9)=24
x....x...
..xx...xx
.........
xx..xxx..
........x
..xx....x
x....xx..
x....xx..
..xx....x

a(10)=28
x.....x...
..xxx...xx
..........
xx...xxx..
...x.....x
...x.....x
xx...xxx..
..........
..xxx...xx
x.....x...