Number of n-step three-sided prudent self-avoiding walks.

Terms

a(0) =1a(1) =4a(2) =12a(3) =34a(4) =90a(5) =236a(6) =612a(7) =1580a(8) =4060a(9) =10404a(10) =26590a(11) =67820a(12) =172654a(13) =438842a(14) =1113808a(15) =2823322a(16) =7148356a(17) =18080002a(18) =45685138a(19) =115337852a(20) =290950252a(21) =733403312a(22) =1847428300a(23) =4650655654a(24) =11700417780a(25) =29420236400a(26) =73937334336a(27) =185724046180