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

Terms

a(0) =1a(1) =4a(2) =12a(3) =36a(4) =100a(5) =276a(6) =748a(7) =2012a(8) =5356a(9) =14172a(10) =37276a(11) =97604a(12) =254508a(13) =661364a(14) =1713292a(15) =4426428a(16) =11408300a(17) =29339324a(18) =75305596a(19) =192945124a(20) =493554916a(21) =1260643868a(22) =3215551292a(23) =8191635220a(24) =20843850764a(25) =52980214316a(26) =134527157780a(27) =341268196780