Number of n-step three-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) =127a(6) =327a(7) =841a(8) =2157a(9) =5523a(10) =14115a(11) =36019a(12) =91779a(13) =233557a(14) =593625a(15) =1507125a(16) =3822395a(17) =9685135a(18) =24518103a(19) =62016309a(20) =156742115a(21) =395865603a(22) =999105203a(23) =2519960799a(24) =6352014717a(25) =16002180569a(26) =40291214021a(27) =101395244925a(28) =255042422247