Number of base 15 n-digit numbers with adjacent digits differing by one or less.

Terms

a(0) =1a(1) =15a(2) =43a(3) =125a(4) =365a(5) =1069a(6) =3137a(7) =9219a(8) =27123a(9) =79869a(10) =235361a(11) =693991a(12) =2047367a(13) =6042659a(14) =17841247a(15) =52694573a(16) =155679885a(17) =460055423a(18) =1359834747a(19) =4020216877a(20) =11887503933a(21) =35156155109a(22) =103985848697a(23) =307611659819a(24) =910083564731