A367250 a(n) is the number of n-digit numbers whose difference between the largest and smallest digits is equal to 9.

0, 1, 35, 703, 11231, 158311, 2062655, 25466743, 302423471, 3487593511, 39314599775, 435241463383, 4748453693711, 51186327429511, 546278900354495, 5781325731101623, 60750456603203951, 634502309615150311, 6592506388026870815, 68188442304165981463, 702543059232886986191

Offset: 1

Author

Stefano Spezia, Nov 11 2023

Keywords

• nonn
• base
• easy

Comments

a(n) is the number of n-digit numbers in A366966.

Links

• Index entries for linear recurrences with constant coefficients, signature (27,-242,720).

Crossrefs

Cf. A366966.

Cf. A001018, A001019, A011557.

Cf. A367243, A367244, A367245, A367246, A367247, A367248, A367249.

Programs

Mathematica

LinearRecurrence[{27,-242,720},{0,1,35},21]

Formula

a(n) = 9*10^(n-1) - 17*9^(n-1) + 8^n.

a(n) = 27*a(n-1) - 242*a(n-2) + 720*a(n-3) for n > 3.

O.g.f.: x^2*(1 + 8*x)/((1 - 8*x)*(1 - 9*x)*(1 - 10*x)).

E.g.f.: (81*exp(10*x) - 170*exp(9*x) + 90*exp(8*x) - 1)/90.