Number of pseudo-square parallelogram (psp) polyominoes by semiperimeter.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =11a(5) =22a(6) =45a(7) =90a(8) =184a(9) =370a(10) =751a(11) =1516a(12) =3053a(13) =6172a(14) =12405a(15) =25042a(16) =50323a(17) =101424a(18) =203880a(19) =410296a(20) =824871a(21) =1658338a(22) =3333405a(23) =6696814a(24) =13457112a(25) =27021758a(26) =54278993a(27) =108952646a(28) =218765704a(29) =439001338