Number of 3D n-step walks of type acc.

Terms

a(0) =1a(1) =2a(2) =7a(3) =24a(4) =98a(5) =400a(6) =1785a(7) =7980a(8) =37674a(9) =178164a(10) =874146a(11) =4294752a(12) =21667932a(13) =109436184a(14) =563910633a(15) =2908233900a(16) =15235550330a(17) =79870553620a(18) =424021948350