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A257286 a(n) = 5*6^n-4*5^n. 2
1, 10, 80, 580, 3980, 26380, 170780, 1087180, 6835580, 42575980, 263268380, 1618672780, 9907349180, 60420657580, 367406757980, 2228854610380, 13495197974780, 81581539411180, 492540994279580, 2970504754739980, 17899322473752380 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

First differences of 6^n-5^n = A005062.

Number of numbers with n digits having the largest digit equal to 5. Or, equivalently, number of n-letter words over a 6-letter alphabet {a,b,c,d,e,f}, which must not start with the first letter of the alphabet, and in which the last letter of the alphabet must appear.

LINKS

Table of n, a(n) for n=0..20.

Index entries for linear recurrences with constant coefficients, signature (11,-30).

FORMULA

a(n) = 11 a(n-1) - 30 a(n-2).

G.f.: (1-x)/((1-5*x)*(1-6*x)). - Vincenzo Librandi, May 04 2015

MATHEMATICA

Table[5 6^n - 4 5^n, {n, 0, 30}] (* Vincenzo Librandi, May 04 2015 *)

PROG

(PARI) a(n)=5*6^n-4*5^n

(MAGMA) [5*6^n-4*5^n: n in [0..20]]; // Vincenzo Librandi, May 04 2015

CROSSREFS

Cf. A005062.

Coincides with A125373 only for the first terms.

See also A000225, A027649, A255463, A257285 - A257289 and A088924.

Sequence in context: A220485 A055285 A036070 * A125373 A093145 A037509

Adjacent sequences:  A257283 A257284 A257285 * A257287 A257288 A257289

KEYWORD

nonn,easy

AUTHOR

M. F. Hasler, May 03 2015

STATUS

approved

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Last modified October 15 00:03 EDT 2019. Contains 328025 sequences. (Running on oeis4.)