A203769 a(n) = (A203768(n+2) - 1)/2.

0, 0, 1, 5, 30, 479, 35369, 36141988, 2591378388181, 187498452473472843625, 971772428248668220494932383712302, 364411657942488572318753161467113186052857526280591219

Offset

1,4

Links

Table of n, a(n) for n=1..12.

Mathematica

a[1] = 0; a[2] = 0; a[3] = 1;
a[n_] := SymmetricPolynomial[2, {a[n - 1], a[n - 2], 1 + a[n - 3]}]
Table[a[n], {n, 1, 16}]  (* A203768 *)
(Rest[Rest[%]] - 1)/2    (* A203769 *)

Crossrefs

Cf. A203761, A203768.

Sequence in context: A380607 A052172 A058783 * A264861 A264864 A297472

Adjacent sequences: A203766 A203767 A203768 * A203770 A203771 A203772

Keyword

nonn

Author

Clark Kimberling, Jan 07 2012

Extensions

Definition corrected by Georg Fischer, May 04 2022

Status

approved