cp's OEIS Frontend

A192817 Numbers that are coprime to their 9's complement.

%I A192817 #52 Sep 08 2022 08:45:58
%S A192817 1,2,4,5,7,8,10,13,14,16,17,19,20,23,25,26,28,29,31,32,34,35,37,38,40,
%T A192817 41,43,46,47,49,50,52,53,56,58,59,61,62,64,65,67,68,70,71,73,74,76,79,
%U A192817 80,82,83,85,86,89,91,92,94,95,97,98,100,101,103,104,106
%N A192817 Numbers that are coprime to their 9's complement.
%C A192817 If an integer is in this sequence, its 9's complement is in the sequence as well. No multiple of 3 is in this sequence. Multiples of 11 are in the sequence if they have an odd number of digits and they are not also multiples of 3.
%H A192817 Reinhard Zumkeller, <a href="/A192817/b192817.txt">Table of n, a(n) for n = 1..10000</a>
%e A192817 25 is in the sequence because its 9's complement is 74 and gcd(25, 74) = 1.
%p A192817 with(numtheory): P:=proc(q) local k,n; for n from 1 to q do for k from 1 to q do
%p A192817 if type(((n-k)*10^(ilog10(n+k)+1)+n+k)/n,integer) then break; fi; od;
%p A192817 if k=n then print(n); fi; od; end: P(10^4); # _Paolo P. Lava_, Nov 03 2014
%t A192817 (* First run the program for A061601 to define nineComplement *) Select[Range[100], GCD[#, nineComplement[#]] == 1 &]
%o A192817 (Magma) [n: n in [1..106] | Gcd(10^#Intseq(n)-1,n) eq 1]; // _Bruno Berselli_, Dec 02 2011
%o A192817 (Haskell)
%o A192817 a192817 n = a192817_list !! (n-1)
%o A192817 a192817_list = [x | x <- [1..], gcd x (a061601 x) == 1]
%o A192817 -- _Reinhard Zumkeller_, Dec 03 2011
%Y A192817 Cf. A061601 (9's complement of n), A201462 (complement).
%K A192817 nonn,easy,base
%O A192817 1,2
%A A192817 _Alonso del Arte_, Dec 01 2011