Number of 1-punctured staircase polygons (by perimeter) with a hole of perimeter 4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =1a(9) =12a(10) =92a(11) =576a(12) =3214a(13) =16664a(14) =82160a(15) =390656a(16) =1807781a(17) =8192524a(18) =36519556a(19) =160645504a(20) =699030226a(21) =3014470024a(22) =12901501696a(23) =54863119744a(24) =232022899306a(25) =976598630968