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A192817
Numbers that are coprime to their 9's complement.
3
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, 41, 43, 46, 47, 49, 50, 52, 53, 56, 58, 59, 61, 62, 64, 65, 67, 68, 70, 71, 73, 74, 76, 79, 80, 82, 83, 85, 86, 89, 91, 92, 94, 95, 97, 98, 100, 101, 103, 104, 106
OFFSET
1,2
COMMENTS
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.
LINKS
EXAMPLE
25 is in the sequence because its 9's complement is 74 and gcd(25, 74) = 1.
MAPLE
with(numtheory): P:=proc(q) local k, n; for n from 1 to q do for k from 1 to q do
if type(((n-k)*10^(ilog10(n+k)+1)+n+k)/n, integer) then break; fi; od;
if k=n then print(n); fi; od; end: P(10^4); # Paolo P. Lava, Nov 03 2014
MATHEMATICA
(* First run the program for A061601 to define nineComplement *) Select[Range[100], GCD[#, nineComplement[#]] == 1 &]
PROG
(Magma) [n: n in [1..106] | Gcd(10^#Intseq(n)-1, n) eq 1]; // Bruno Berselli, Dec 02 2011
(Haskell)
a192817 n = a192817_list !! (n-1)
a192817_list = [x | x <- [1..], gcd x (a061601 x) == 1]
-- Reinhard Zumkeller, Dec 03 2011
CROSSREFS
Cf. A061601 (9's complement of n), A201462 (complement).
Sequence in context: A363761 A363763 A189303 * A229968 A190853 A343108
KEYWORD
nonn,easy,base
AUTHOR
Alonso del Arte, Dec 01 2011
STATUS
approved