A199687 a(n) = 7*10^n + 1.
8, 71, 701, 7001, 70001, 700001, 7000001, 70000001, 700000001, 7000000001, 70000000001, 700000000001, 7000000000001, 70000000000001, 700000000000001, 7000000000000001, 70000000000000001, 700000000000000001, 7000000000000000001, 70000000000000000001, 700000000000000000001
Offset: 0
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..1000
- Index entries for linear recurrences with constant coefficients, signature (11,-10).
Programs
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Magma
[7*10^n+1: n in [0..30]];
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Mathematica
7*10^Range[0,20]+1 (* or *) LinearRecurrence[{11,-10},{8,71},20] (* Harvey P. Dale, May 29 2018 *)
Formula
a(n) = 10*a(n-1) - 9.
a(n) = 11*a(n-1) - 10*a(n-2).
G.f.: (8-17*x)/((1-x)*(1-10*x)).
E.g.f.: exp(x)*(1 + 7*exp(9*x)). - Elmo R. Oliveira, Jun 10 2025