Number of permutations of length n which avoid the patterns 1234, 4312.

Terms

a(0) =1a(1) =2a(2) =6a(3) =22a(4) =86a(5) =321a(6) =1085a(7) =3266a(8) =8797a(9) =21478a(10) =48206a(11) =100728a(12) =198046a(13) =369617a(14) =659505a(15) =1131656a(16) =1876481a(17) =3018946a(18) =4728382a(19) =7230242a(20) =10820046a(21) =15879769a(22) =22896941a(23) =32486742a(24) =45417389a(25) =62639126a(26) =85317142a(27) =114868756a(28) =153005222a(29) =201778521