Number of (n+1)-extended Skolem sequences of order n.

Terms

a(0) =0a(1) =0a(2) =2a(3) =2a(4) =0a(5) =0a(6) =44a(7) =260a(8) =0a(9) =0a(10) =33104a(11) =203712a(12) =0a(13) =0a(14) =75499696a(15) =621309008a(16) =0a(17) =0a(18) =492805156768a(20) =0a(21) =0