Number of permutations of [n] with four inversions.

Terms

a(0) =5a(1) =20a(2) =49a(3) =98a(4) =174a(5) =285a(6) =440a(7) =649a(8) =923a(9) =1274a(10) =1715a(11) =2260a(12) =2924a(13) =3723a(14) =4674a(15) =5795a(16) =7105a(17) =8624a(18) =10373a(19) =12374a(20) =14650a(21) =17225a(22) =20124a(23) =23373a(24) =26999a(25) =31030a(26) =35495a(27) =40424a(28) =45848a(29) =51799