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 A138120 Concatenation of n digits 1, 2n-1 digits 0 and n digits 1. 15
 101, 1100011, 11100000111, 111100000001111, 1111100000000011111, 11111100000000000111111, 111111100000000000001111111, 1111111100000000000000011111111, 11111111100000000000000000111111111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) has 4n-1 digits. a(n) is also A147539(n) written in base 2. [From Omar E. Pol, Nov 08 2008] LINKS Index entries for linear recurrences with constant coefficients, signature (11011,-10121010,110110000,-100000000). FORMULA a(n)={(10^n-1)*[1+10^(3n-1)]}/9, with n>=1 [From Paolo P. Lava, Nov 26 2008] G.f.: x*(10001000*x^2-12100*x+101) / ((x-1)*(10*x-1)*(1000*x-1)*(10000*x-1)). [Colin Barker, Sep 16 2013] EXAMPLE n ........... a(n) 1 ........... 101 2 ......... 1100011 3 ....... 11100000111 4 ..... 111100000001111 5 ... 1111100000000011111 MATHEMATICA Table[FromDigits[Join[PadRight[{}, n, 1], PadRight[{}, 2n-1, 0], PadRight[ {}, n, 1]]], {n, 10}] (* or *) LinearRecurrence[{11011, -10121010, 110110000, -100000000}, {101, 1100011, 11100000111, 111100000001111}, 10] (* Harvey P. Dale, Mar 19 2016 *) PROG (PARI) Vec(x*(10001000*x^2-12100*x+101)/((x-1)*(10*x-1)*(1000*x-1)*(10000*x-1)) + O(x^100)) \\ Colin Barker, Sep 16 2013 CROSSREFS Cf. A138144, A138145, A138146, A138148, A138720, A138721, A138722, A138826. Cf. A147539. [From Omar E. Pol, Nov 08 2008] Sequence in context: A015041 A317957 A266244 * A266609 A082521 A262645 Adjacent sequences:  A138117 A138118 A138119 * A138121 A138122 A138123 KEYWORD base,easy,nonn AUTHOR Omar E. Pol, Apr 06 2008 STATUS approved

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Last modified July 25 12:15 EDT 2021. Contains 346290 sequences. (Running on oeis4.)