A216099 Period of powers of 3 mod 10^n.
4, 20, 100, 500, 5000, 50000, 500000, 5000000, 50000000, 500000000, 5000000000, 50000000000, 500000000000, 5000000000000, 50000000000000, 500000000000000, 5000000000000000, 50000000000000000, 500000000000000000
Offset: 1
Links
- Index entries for linear recurrences with constant coefficients, signature (10).
Programs
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Mathematica
Table[If[n<5,(4*5^n)/5,10^n/20],{n,20}] (* or *) Join[{4,20,100},NestList[ 10#&,500,20]] (* Harvey P. Dale, May 31 2017 *) -
PARI
a(n)=if(n<5,4*5^n/5,10^n/20) \\ Charles R Greathouse IV, Mar 26 2016
Formula
a(n) = 4*5^(n-1) for n <= 4.
a(n) = 5*10^(n-2) for n >= 5.
Comments