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A192817
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Numbers that are coprime to their 9's complement.
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3
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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
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OFFSET
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1,2
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COMMENTS
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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.
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LINKS
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EXAMPLE
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25 is in the sequence because its 9's complement is 74 and gcd(25, 74) = 1.
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MAPLE
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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
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MATHEMATICA
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(* First run the program for A061601 to define nineComplement *) Select[Range[100], GCD[#, nineComplement[#]] == 1 &]
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PROG
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(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]
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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