a(n) = F(n)^2 - F(n-1)^2 or F(n+1) * F(n-2) where F(n) = A000045(n), the Fibonacci numbers.

Terms

a(0) =1a(1) =0a(2) =3a(3) =5a(4) =16a(5) =39a(6) =105a(7) =272a(8) =715a(9) =1869a(10) =4896a(11) =12815a(12) =33553a(13) =87840a(14) =229971a(15) =602069a(16) =1576240a(17) =4126647a(18) =10803705a(19) =28284464a(20) =74049691a(21) =193864605a(22) =507544128a(23) =1328767775a(24) =3478759201a(25) =9107509824a(26) =23843770275a(27) =62423800997a(28) =163427632720a(29) =427859097159