A126506 Number of base 11 n-digit numbers with adjacent digits differing by four or less.

1, 11, 79, 591, 4441, 33391, 251077, 1887941, 14196143, 106746189, 802665137, 6035544031, 45383547985, 341256134861, 2566034493807, 19294987989285, 145086343307233, 1090959321972847, 8203337509713921, 61684010524412861

Offset: 0

Author

R. H. Hardin, Dec 28 2006

Keywords

• nonn
• base

Comments

[Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4.

Crossrefs

Cf. Base 11 differing by three or less A126479, two or less A126398, one or less A126365.

Formula

G.f.: (1-x-x^2)*(1+4*x-2*x^2-4*x^3+2*x^4) / ((1-x)*(1-7*x-5*x^2+8*x^3+2*x^4-2*x^5)) (conjectured). - Colin Barker, Jul 17 2017