Increase in the number of fixed polyominoes from order n to order n+1.

Terms

a(0) =0a(1) =1a(2) =4a(3) =13a(4) =44a(5) =153a(6) =544a(7) =1965a(8) =7185a(9) =26536a(10) =98822a(11) =370593a(12) =1398029a(13) =5300984a(14) =20189792a(15) =77198271a(16) =296202907a(17) =1140024698a(18) =4399918134a(19) =17024040984a(20) =66018733123a(21) =256549059895a(22) =998839762846