Number of permutations (p(1),p(2),...,p(n)) of (1,2,...,n) such that p(i)-i is in {-2,0,5} for all i=1,...,n.
A387020
Number of permutations (p(1),p(2),...,p(n)) of (1,2,...,n) such that p(i)-i is in {-2,0,5} for all i=1,...,n.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =2a(8) =3a(9) =5a(10) =7a(11) =10a(12) =13a(13) =16a(14) =20a(15) =25a(16) =34a(17) =46a(18) =67a(19) =94a(20) =130a(21) =175a(22) =231a(23) =305a(24) =400a(25) =540a(26) =729a(27) =999a(28) =1363a(29) =1855
External references
- oeis: A387020