Bisection of A099924 (convolution of Lucas numbers); even arguments.

Terms

a(0) =4a(1) =13a(2) =45a(3) =152a(4) =491a(5) =1531a(6) =4652a(7) =13865a(8) =40713a(9) =118144a(10) =339559a(11) =968183a(12) =2742100a(13) =7721797a(14) =21637221a(15) =60367976a(16) =167787107a(17) =464776435a(18) =1283571068a(19) =3535240289a(20) =9713031489a(21) =26627195728a(22) =72847698655a(23) =198929987567a(24) =542305383076