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 A002276 a(n) = 2*(10^n - 1)/9. 38
 0, 2, 22, 222, 2222, 22222, 222222, 2222222, 22222222, 222222222, 2222222222, 22222222222, 222222222222, 2222222222222, 22222222222222, 222222222222222, 2222222222222222, 22222222222222222, 222222222222222222, 2222222222222222222 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) = A178630(n)/A002283(n). - Reinhard Zumkeller, May 31 2010 a(n) is also the total number of holes in a variation of a box fractal as in illustration. - Kival Ngaokrajang, May 23 2014 [As observed by Hans Havermann, this seems to be incorrect: e.g., for n = 2 the illustration shows 28 small holes plus two larger holes. - M. F. Hasler, Oct 05 2020] LINKS Ivan Panchenko, Table of n, a(n) for n = 0..200 Kival Ngaokrajang, Illustration for n = 1..4 Index entries for linear recurrences with constant coefficients, signature (11,-10). FORMULA a(n) = 10*a(n-1) + 2, with a(0) = 0. - Paolo P. Lava, Jan 23 2009 a(n) = a(n-1) + 2*10^(n-1) with a(0) = 0; Also: a(n) = 11*a(n-1) - 10*a(n-2) with a(0) = 0, a(1) = 2. - Vincenzo Librandi, Jul 22 2010 G.f.: 2*x/((1 - x)*(1 - 10*x)). - Ilya Gutkovskiy, Feb 24 2017 MATHEMATICA LinearRecurrence[{11, -10}, {0, 2}, 50] (* Jinyuan Wang, Feb 27 2020 *) PROG (Maxima) A002276(n):=2*(10^n - 1)/9\$ makelist(A002276(n), n, 0, 20); /* Martin Ettl, Nov 12 2012 */ (PARI) a(n)=10^n\9*2 \\ M. F. Hasler, Mar 27 2015 CROSSREFS Cf. A002275, A002277, A002278, A002279, A002280, A002281, A002282, A178634. Sequence in context: A037567 A174200 A137109 * A112893 A086855 A089182 Adjacent sequences:  A002273 A002274 A002275 * A002277 A002278 A002279 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified April 22 19:11 EDT 2021. Contains 343177 sequences. (Running on oeis4.)