Number of permutations of 3 indistinguishable copies of 1,...,n such that the first and second copies of j are adjacent and there are exactly j numbers between the second and the third copy of j.
A264813
Number of permutations of 3 indistinguishable copies of 1,...,n such that the first and second copies of j are adjacent and there are exactly j numbers between the second and the third copy of j.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =0a(5) =3a(6) =6a(7) =0a(8) =53a(9) =199a(10) =0a(11) =2908a(12) =13699a(13) =0a(14) =369985a(15) =2135430a(16) =0a(17) =87265700a(18) =611286653a(19) =0a(20) =34928617573a(21) =284205647124a(22) =0
External references
- oeis: A264813