Number of ascending runs in {1,...,4}^n.

Terms

a(0) =0a(1) =4a(2) =26a(3) =144a(4) =736a(5) =3584a(6) =16896a(7) =77824a(8) =352256a(9) =1572864a(10) =6946816a(11) =30408704a(12) =132120576a(13) =570425344a(14) =2449473536a(15) =10468982784a(16) =44560285696a(17) =188978561024a(18) =798863917056