a(n) = F(n+4) * F(n+2) + 7 * (-1)^n where F(n) = A000045(n) are the Fibonacci numbers.

Terms

a(0) =3a(1) =31a(2) =58a(3) =175a(4) =435a(5) =1162a(6) =3019a(7) =7927a(8) =20730a(9) =54295a(10) =142123a(11) =372106a(12) =974163a(13) =2550415a(14) =6677050a(15) =17480767a(16) =45765219a(17) =119814922a(18) =313679515a(19) =821223655a(20) =2149991418a(21) =5628750631a(22) =14736260443a(23) =38580030730a(24) =101003831715a(25) =264431464447a(26) =692290561594