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A231471
Largest integer less than 11 and coprime to n.
4
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
OFFSET
1,1
COMMENTS
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
LINKS
EXAMPLE
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.
MAPLE
f:= proc(n) local k;
for k from 10 by -1 do if igcd(n, k)=1 then return k fi od
end proc:
map(f, [$1..210]); # Robert Israel, Jul 03 2020
MATHEMATICA
Table[m = 10; While[GCD[m, n] != 1, m--]; m, {n, 75}] (* Alonso del Arte, Nov 09 2013 *)
PROG
(PARI) a(n, m=11)=for(k=1, m, gcd(n, m-k)==1&&return(m-k))
CROSSREFS
Cf. A231475 (analog for 5), A231470 (analog for 10), A231155.
Sequence in context: A070562 A216557 A070641 * A063661 A154533 A167608
KEYWORD
nonn,easy,changed
AUTHOR
M. F. Hasler, Nov 09 2013
STATUS
approved