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A257288 a(n) = 7*8^n-6*7^n. 1
1, 14, 154, 1526, 14266, 128534, 1129114, 9738806, 82851706, 697402454, 5821341274, 48265581686, 397988613946, 3266956634774, 26716987140634, 217805235562166, 1770927253556986, 14366815611873494, 116330307978911194, 940412945418752246, 7591696934462256826 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

First differences of 8^n-7^n = A016177.

Number of numbers with n digits having the largest digit equal to 7. Note that this is independent of the base b > 7.

Equivalently, number of n-letter words over a 8-letter alphabet, which must not start with the last letter of the alphabet, and in which the first letter of the alphabet must appear.

LINKS

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

FORMULA

G.f.: (1-x)/((1-7*x)*(1-8*x)). - Vincenzo Librandi, May 04 2015

MATHEMATICA

Table[7 8^n - 6 7^n, {n, 0, 30}] (* Vincenzo Librandi, May 04 2015 *)

PROG

(PARI) a(n)=7*8^n-6*7^n

(MAGMA) [7*8^n-6*7^n: n in [0..20]]; // Vincenzo Librandi, May 04 2015

CROSSREFS

Cf. A016177.

Sequence in context: A290675 A097227 A229315 * A125426 A004986 A154248

Adjacent sequences:  A257285 A257286 A257287 * A257289 A257290 A257291

KEYWORD

nonn,easy

AUTHOR

M. F. Hasler, May 03 2015

STATUS

approved

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Last modified July 18 21:25 EDT 2019. Contains 325144 sequences. (Running on oeis4.)