a(n) = Lucas(4n+3) - 1, or Lucas(2n+1)*Lucas(2n+2).

A081019

a(n) = Lucas(4n+3) - 1, or Lucas(2n+1)*Lucas(2n+2).

Terms

    a(0) =3a(1) =28a(2) =198a(3) =1363a(4) =9348a(5) =64078a(6) =439203a(7) =3010348a(8) =20633238a(9) =141422323a(10) =969323028a(11) =6643838878a(12) =45537549123a(13) =312119004988

External references