A319879 - OEIS

%I #14 Jul 01 2019 12:12:53

%S 1,8,13,18,21,26,29,34,37,40,45,48,51,56,59,62,65,70,73,76,79,84,87,

%T 90,93,96,101,104,107,110,113,118,121,124,127,130,133,138,141,144,147,

%U 150,153,158,161,164,167,170,173,176,181

%N a(n) = minimal number m of unit squares needed to make an figure formed from squares (joined edge to edge) which has n holes.

%C The holes must not touch each other.

%D Jean-Paul Delahaye, Des trous à entourer avec parcimonie, Pour las science, No. 501, Juillet 2019, pp. 82-87.

%e Examples from _N. J. A. Sloane_, Jan 30 2019 for n=1, 2, 3:

%e XXX

%e XOX

%e XXX

%e ---

%e XXXXX

%e XOXOX

%e XXXXX

%e -----

%e XXXXXXX

%e XOXOXOX

%e XXXXXXX

%K nonn

%O 0,2

%A _Jean-Paul Delahaye_, Sep 30 2018

%E Entry 123 changed to 124 by the author, Jul 01 2019. - _N. J. A. Sloane_, Jul 01 2019