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A155872 a(n) = 10^n + 11^n. 2
2, 21, 221, 2331, 24641, 261051, 2771561, 29487171, 314358881, 3357947691, 35937424601, 385311670611, 4138428376721, 44522712143931, 479749833583241, 5177248169415651, 55949729863572161, 605447028499293771 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) gives the combined total number of n digit numbers [preceding zeros allowed] in base 10 and 11

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..900

Index entries for linear recurrences with constant coefficients, signature (21,-110).

FORMULA

G.f.: 1/(1-10*x) + 1/(1-11*x). - Vincenzo Librandi, Feb 06 2013

MATHEMATICA

CoefficientList[Series[1/(1 - 10 x) + 1/(1 - 11 x), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 06 2013 *)

LinearRecurrence[{21, -110}, {2, 21}, 20] (* Harvey P. Dale, Aug 27 2020 *)

PROG

(MAGMA) [10^n+11^n: n in [0..30]]; // Vincenzo Librandi, Feb 06 2013

CROSSREFS

Sequence in context: A109684 A292134 A137287 * A323478 A106412 A329497

Adjacent sequences:  A155869 A155870 A155871 * A155873 A155874 A155875

KEYWORD

nonn,easy

AUTHOR

Avik Roy (avik_3.1416(AT)yahoo.co.in), Jan 29 2009

STATUS

approved

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Last modified April 21 11:10 EDT 2021. Contains 343150 sequences. (Running on oeis4.)