A173806 a(n) = (7*10^n - 61)/9 for n > 0.
1, 71, 771, 7771, 77771, 777771, 7777771, 77777771, 777777771, 7777777771, 77777777771, 777777777771, 7777777777771, 77777777777771, 777777777777771, 7777777777777771, 77777777777777771, 777777777777777771, 7777777777777777771, 77777777777777777771, 777777777777777777771
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..100
- Index entries for linear recurrences with constant coefficients, signature (11,-10).
Crossrefs
Cf. A093176.
Programs
-
Magma
[(7*10^n-61)/9: n in [1..20]]; // Vincenzo Librandi, Jul 05 2012
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Mathematica
CoefficientList[Series[(1+60*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* Vincenzo Librandi, Jul 05 2012 *)
Formula
a(n) = 10*a(n-1) + 61 with n > 0, a(0)=-6.
From Vincenzo Librandi, Jul 05 2012: (Start)
G.f.: x*(1+60*x)/((1-x)*(1-10*x)).
a(n) = 11*a(n-1) - 10*a(n-2) for n > 2. (End)
E.g.f.: 6 + exp(x)*(7*exp(9*x) - 61)/9. - Elmo R. Oliveira, Sep 09 2024