a(0)=0, a(1)=1, a(n)=4a(n-1)+2 for n =3,5,7,..., a(n)=4a(n-1) for n =2,4,6,....

A117615

a(0)=0, a(1)=1, a(n)=4a(n-1)+2 for n =3,5,7,..., a(n)=4a(n-1) for n =2,4,6,....

Terms

    a(0) =0a(1) =1a(2) =4a(3) =18a(4) =72a(5) =290a(6) =1160a(7) =4642a(8) =18568a(9) =74274a(10) =297096a(11) =1188386a(12) =4753544a(13) =19014178a(14) =76056712a(15) =304226850a(16) =1216907400a(17) =4867629602a(18) =19470518408a(19) =77882073634a(20) =311528294536

External references