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 A138147 Concatenation of n digits 1 and n digits 0. 8
 10, 1100, 111000, 11110000, 1111100000, 111111000000, 11111110000000, 1111111100000000, 111111111000000000, 11111111110000000000, 1111111111100000000000, 111111111111000000000000, 11111111111110000000000000, 1111111111111100000000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also, a(n) = binary representation of A020522(n), for n>0 (see example). REFERENCES J.-P. Allouche and J. Shallit, Automatic Sequences, Cambridge Univ. Press, 2003, p. 136, Ex. 4.2.2. - N. J. A. Sloane, Jul 27 2012 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..95 Index entries for linear recurrences with constant coefficients, signature (110,-1000). FORMULA a(n) = (10^(2n) - 10^n)/9 = A002275(n)*10^n. - Omar E. Pol, Apr 16 2008 a(n) = A109241(n-1)*10. - Omar E. Pol, Nov 08 2008 From Colin Barker, Sep 16 2013: (Start) a(n) = 110*a(n-1) - 1000*a(n-2). G.f.: 10*x / ((10*x-1)*(100*x-1)). (End) EXAMPLE n ... A020522(n) ..... a(n) 1 ....... 2 ........... 10 2 ...... 12 .......... 1100 3 ...... 56 ......... 111000 4 ..... 240 ........ 11110000 5 ..... 992 ....... 1111100000 6 .... 4032 ...... 111111000000 7 ... 16256 ..... 11111110000000 MATHEMATICA Table[FromDigits[Join[PadRight[{}, n, 1], PadRight[{}, n, 0]]], {n, 15}] (* Harvey P. Dale, Nov 20 2011 *) PROG (MAGMA) [(10^(2*n) - 10^n)/9: n in [1..30]]; // Vincenzo Librandi, Apr 26 2011 (PARI) Vec(10*x/((10*x-1)*(100*x-1)) + O(x^100)) \\ Colin Barker, Sep 16 2013 CROSSREFS Cf. A020522, A138144, A138145, A138720. Cf. A002275. Cf. A109241, A138118, A138119, A138120, A138146, A138721, A138826. - Omar E. Pol, Nov 08 2008 Sequence in context: A290155 A265849 A122230 * A204577 A210995 A325910 Adjacent sequences:  A138144 A138145 A138146 * A138148 A138149 A138150 KEYWORD easy,nonn,base AUTHOR Omar E. Pol, Mar 29 2008 STATUS approved

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Last modified April 20 15:38 EDT 2021. Contains 343135 sequences. (Running on oeis4.)