A126486 Number of base 18 n-digit numbers with adjacent digits differing by three or less.

1, 18, 114, 742, 4874, 32186, 213226, 1415510, 9409592, 62605198, 416772336, 2775553058, 18488673878, 123177305178, 820730049614, 5468888194572, 36443213300730, 242854735692378, 1618394841578240, 10785184848010492

Offset

0,2

Comments

[Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3.

Links

Table of n, a(n) for n=0..19.

Formula

G.f.: (1+7*x-58*x^2-12*x^3+169*x^4-3*x^5-128*x^6+3*x^7+24*x^8) / (1-11*x+26*x^2+32*x^3-83*x^4-21*x^5+64*x^6+3*x^7-12*x^8) (conjectured). - Colin Barker, Jul 18 2017

Prog

(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))

Crossrefs

Cf. Base 18 differing by two or less A126405, one or less A126372.

Sequence in context: A324623 A244866 A125328 * A251937 A061803 A207103

Adjacent sequences: A126483 A126484 A126485 * A126487 A126488 A126489

Keyword

nonn,base

Author

R. H. Hardin, Dec 27 2006

Status

approved