Number of n-step four-sided prudent self-avoiding walks ending on the top side of their box.

Terms

a(0) =1a(1) =3a(2) =7a(3) =19a(4) =49a(5) =129a(6) =333a(7) =865a(8) =2233a(9) =5763a(10) =14825a(11) =38087a(12) =97641a(13) =249961a(14) =638861a(15) =1630681a(16) =4156737a(17) =10583483a(18) =26916167a(19) =68383509a(20) =173565889a(21) =440133159a(22) =1115145081a(23) =2823128197a(24) =7141682287a(25) =18053470305a(26) =45606579731a(27) =115137581735a(28) =290498368253