a(n) = 1*4^n + 2*3^n + 3*2^n + 4*1^n.

Terms

a(0) =10a(1) =20a(2) =50a(3) =146a(4) =470a(5) =1610a(6) =5750a(7) =21146a(8) =79430a(9) =303050a(10) =1169750a(11) =4554746a(12) =17852390a(13) =70322090a(14) =278050550a(15) =1102537946a(16) =4381257350a(17) =17438542730a(18) =69495104150a(19) =277204002746