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 A059988 a(n) = (10^n - 1)^2. 18
 0, 81, 9801, 998001, 99980001, 9999800001, 999998000001, 99999980000001, 9999999800000001, 999999998000000001, 99999999980000000001, 9999999999800000000001, 999999999998000000000001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Comment from James D. Klein, Feb 05 2012: (Start) The periods of the reciprocals of a(n) are the consecutive integers from 0 to 10^n-1, omitting the one integer 10^n-2, right-justified in field widths of size n. E.g.: 1/81 = 0.012345679... 1/9801 = 0.000102030405060708091011...9799000102... 1/998001 = 0.000001002003004005...997999000001002... (End) Sum of first 10^n - 1 odd numbers. - Arkadiusz Wesolowski, Jun 12 2013 REFERENCES Walther Lietzmann, Lustiges und Merkwuerdiges von Zahlen und Formen, (F. Hirt, Breslau 1921-43), p. 149. LINKS Harry J. Smith, Table of n, a(n) for n = 0..200 FORMULA a(n) = 81*A002477(n) = A002283(n)^2 = (9*A002275(n))^2. a(n) = {999... (n times)}^2 = {999... (n times), 000... (n times)} - {999... (n times)}. For example, 999^2 = 999000 - 999 = 998001. - Kyle D. Balliet, Mar 07 2009 n>0: a(n) = (A002283(n-1)*10 + 8) * 10^(n-1) + 1. - Reinhard Zumkeller, May 31 2010 From Ilya Gutkovskiy, Apr 19 2016: (Start) O.g.f.: 81*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). E.g.f.: (1 - 2*exp(9*x) + exp(99*x))*exp(x). (End) EXAMPLE From Reinhard Zumkeller, May 31 2010: (Start) n=1: ..................... 81 = 9^2; n=2: ................... 9801 = 99^2; n=3: ................. 998001 = 999^2; n=4: ............... 99980001 = 9999^2; n=5: ............. 9999800001 = 99999^2; n=6: ........... 999998000001 = 999999^2; n=7: ......... 99999980000001 = 9999999^2; n=8: ....... 9999999800000001 = 99999999^2; n=9: ..... 999999998000000001 = 999999999^2. (End) MAPLE A059988:=n->(10^n-1)^2; seq(A059988(n), n=0..20); # Wesley Ivan Hurt, Nov 21 2013 MATHEMATICA Table[(10^n-1)^2, {n, 0, 20}] (* Wesley Ivan Hurt, Nov 21 2013 *) PROG (PARI) { for (n=0, 200, write("b059988.txt", n, " ", (10^n - 1)^2); ) } \\ Harry J. Smith, Jul 01 2009 CROSSREFS Cf. A075411, A075412, A075413, A075414, A075415, A075416, A075417, A178630, A178631, A178632, A178633, A178634, A178635, A272066, A272067, A272068. Sequence in context: A034993 A223328 A093281 * A017020 A237027 A185847 Adjacent sequences:  A059985 A059986 A059987 * A059989 A059990 A059991 KEYWORD easy,nonn AUTHOR Henry Bottomley, Mar 07 2001 STATUS approved

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Last modified April 17 23:03 EDT 2021. Contains 343071 sequences. (Running on oeis4.)