Number of words of length 2n+1 with one 0 entry and two entries of each of 1..n so that there are exactly k numbers between two equal k's and so that the first element is not 0 and also does not exceed the last.
A381760
Number of words of length 2n+1 with one 0 entry and two entries of each of 1..n so that there are exactly k numbers between two equal k's and so that the first element is not 0 and also does not exceed the last.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =11a(5) =38a(6) =130a(7) =638a(8) =4158a(9) =23384a(10) =124520a(11) =847484a(12) =6987380a(13) =53746000a(14) =400346544a(15) =3529108816a(16) =35963592624a(17) =351432650816
External references
- oeis: A381760