Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i, p(1) <= 3, and p(4) >= 2.
A188491
Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i, p(1) <= 3, and p(4) >= 2.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =6a(4) =14a(5) =48a(6) =152a(7) =476a(8) =1425a(9) =4340a(10) =13288a(11) =40852a(12) =125124a(13) =382888a(14) =1171612a(15) =3587505a(16) =10985790a(17) =33638142a(18) =102988410a(19) =315318756a(20) =965432832a(21) =2955964296a(22) =9050522241a(23) =27710613432a(24) =84843476928a(25) =259771465608a(26) =795361704776
External references
- oeis: A188491