Number of permutations of length n which avoid the patterns 1234, 2431, 3421.

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =73a(5) =222a(6) =563a(7) =1226a(8) =2376a(9) =4213a(10) =6972a(11) =10923a(12) =16371a(13) =23656a(14) =33153a(15) =45272a(16) =60458a(17) =79191a(18) =101986a(19) =129393a(20) =161997a(21) =200418a(22) =245311a(23) =297366a(24) =357308a(25) =425897a(26) =503928a(27) =592231a(28) =691671a(29) =803148