A126394 Number of base 7 n-digit numbers with adjacent digits differing by two or less.

1, 7, 29, 125, 543, 2363, 10287, 44787, 194995, 848979, 3696331, 16093291, 70067867, 305065387, 1328210699, 5782837835, 25177641963, 109619822123, 477268896747, 2077959947307, 9047137938475, 39389933855019

Offset: 0

Author

R. H. Hardin, Dec 28 2006

Keywords

• nonn
• base

Comments

a(base,n)=a(base-1,n)+5^(n-1) for base>=2n-1; a(base,n)=a(base-1,n)+5^(n-1)-2 when base=2n-2.

Links

• Sergey Kitaev, Jeffrey Remmel, (a,b)-rectangle patterns in permutations and words, arXiv:1304.4286 [math.CO], 2013.
• Index entries for linear recurrences with constant coefficients, signature (5,-2,-4,2).

Crossrefs

Cf. Base 7 differing by one or less A126361.

Formula

G.f.: 1 -x*(7-6*x-6*x^2+4*x^3) / ( (x-1)*(2*x^3-2*x^2-4*x+1) ). - R. J. Mathar, Jun 06 2013