Number of 1243-avoiding even Grassmannian permutations of size n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =6a(5) =12a(6) =20a(7) =32a(8) =47a(9) =67a(10) =91a(11) =121a(12) =156a(13) =198a(14) =246a(15) =302a(16) =365a(17) =437a(18) =517a(19) =607a(20) =706a(21) =816a(22) =936a(23) =1068a(24) =1211a(25) =1367a(26) =1535a(27) =1717a(28) =1912a(29) =2122