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A231471
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Largest integer less than 11 and coprime to n.
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4
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10, 9, 10, 9, 9, 7, 10, 9, 10, 9, 10, 7, 10, 9, 8, 9, 10, 7, 10, 9, 10, 9, 10, 7, 9, 9, 10, 9, 10, 7, 10, 9, 10, 9, 9, 7, 10, 9, 10, 9, 10, 5, 10, 9, 8, 9, 10, 7, 10, 9, 10, 9, 10, 7, 9, 9, 10, 9, 10, 7, 10, 9, 10, 9, 9, 7, 10, 9, 10, 9, 10, 7, 10, 9, 8, 9, 10, 7, 10, 9
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OFFSET
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1,1
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COMMENTS
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Motivated by the m = 10 analog A231470 which in turn was motivated by A231155, simply a repetition of (n-1) times the same digit A231470(n).
Periodic with period 210. Possible values are 1, 5, 7, 8, 9, 10. - Robert Israel, Jul 03 2020
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LINKS
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EXAMPLE
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a(1) = 10 because 10 is the largest integer less than 11 and it's coprime to 1.
a(2) = 9 because 10 is not coprime to 2 but 9 is.
a(6) = 7 because 10, 9 and 8 are not coprime to 6 = 2*3.
a(210) = 1 because 210 = 2*3*5*7 is not coprime to any number n > 1, n < 11.
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MAPLE
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f:= proc(n) local k;
for k from 10 by -1 do if igcd(n, k)=1 then return k fi od
end proc:
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MATHEMATICA
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Table[m = 10; While[GCD[m, n] != 1, m--]; m, {n, 75}] (* Alonso del Arte, Nov 09 2013 *)
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PROG
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(PARI) a(n, m=11)=for(k=1, m, gcd(n, m-k)==1&&return(m-k)))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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