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 A138721 Concatenation of n digits 1, n digits 0 and n digits 1. 14
 101, 110011, 111000111, 111100001111, 111110000011111, 111111000000111111, 111111100000001111111, 111111110000000011111111, 111111111000000000111111111, 111111111100000000001111111111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is also A145641(n) written in base 2. - Omar E. Pol, Oct 15 2008 a(n) has 3n digits. - Omar E. Pol, Nov 12 2008 LINKS Index entries for linear recurrences with constant coefficients, signature (1111,-112110,1111000,-1000000). FORMULA a(n+1) = 1000*(a(n)-(10^n-1)/9) + 10^(2*n+2) + (10^(n+1)-1)/9, with a(0)=101 and n >= 1. - Paolo P. Lava, Apr 16 2008 a(n) = -1/9 + (10/9)*10^n - (100/9)*100^n + (1000/9)*1000^n, n >= 0. - Paolo P. Lava, Oct 09 2008 G.f.: x*(101000*x^2 - 2200*x + 101) / ((x-1)*(10*x-1)*(100*x-1)*(1000*x-1)). - Colin Barker, Sep 16 2013 EXAMPLE From Omar E. Pol, Nov 12 2008: (Start) n         Successive digits of a(n) 1                 ( 1 0 1 ) 2              ( 1 1 0 0 1 1 ) 3           ( 1 1 1 0 0 0 1 1 1 ) 4        ( 1 1 1 1 0 0 0 0 1 1 1 1 ) 5     ( 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1 ) (End) MAPLE P:=proc(n) local a, i; a:=101; print(a); for i from 1 by 1 to n do a:=(a-(10^i-1)/9)*1000+10^(2*i+2)+(10^(i+1)-1)/9; print(a); od; end: P(100); # Paolo P. Lava, Apr 16 2008 PROG (PARI) Vec(x*(101000*x^2-2200*x+101)/((x-1)*(10*x-1)*(100*x-1)*(1000*x-1)) + O(x^100)) \\ Colin Barker, Sep 16 2013 CROSSREFS Cf. A000533, A135577, A138120, A138144, A138145, A138146, A138826, A145641, A147757, A147759. Sequence in context: A261966 A076127 A180053 * A068659 A252491 A015078 Adjacent sequences:  A138718 A138719 A138720 * A138722 A138723 A138724 KEYWORD nonn,base,easy AUTHOR Omar E. Pol, Mar 29 2008 STATUS approved

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Last modified May 22 06:32 EDT 2019. Contains 323478 sequences. (Running on oeis4.)