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%I #6 Jul 18 2017 12:29:14
%S 0,1,2,3,-1,6,9,5,7,18,27,-1,-1,-1,54,4,11,15,21,19,8,81,-1,33,-1,57,
%T -1,162,243,29,-1,45,63,-1,55,486,729,-1,87,-1,-1,-1,165,-1,1458,10,
%U 83,249,99,22,17,171,489,163,20,2187,-1,-1,-1,135,-1,189,-1,-1
%N Square array T(n,k) (n>0, k>0) read by antidiagonals: if gcd(n,k)>1 then T(n,k)=-1, otherwise T(n,k) = the unique m such that A289815(m) = n and A289816(m) = k.
%C This sequence, when restricted to the pairs of coprime numbers, is the inverse of the function n -> (A289815(n), A289816(n)).
%C If n and k are coprime, then the number of nonzero digits of the ternary representation of T(n,k) equals the number of distinct prime factors of n*k.
%H Rémy Sigrist, <a href="/A289905/b289905.txt">Table of n, a(n) for n = 1..5050</a>
%H Rémy Sigrist, <a href="/A289905/a289905.gp.txt">PARI program for A289905</a>
%e The table begins:
%e x\y: 1 2 3 4 5 6 7 8 ...
%e 1: 0 2 6 18 54 8 162 486 ...
%e 2: 1 -1 7 -1 19 -1 55 -1 ...
%e 3: 3 5 -1 21 57 -1 165 489 ...
%e 4: 9 -1 15 -1 63 -1 171 -1 ...
%e 5: 27 11 33 45 -1 17 189 513 ...
%e 6: 4 -1 -1 -1 22 -1 58 -1 ...
%e 7: 81 29 87 99 135 35 -1 567 ...
%e 8: 243 -1 249 -1 297 -1 405 -1 ...
%e ...
%o See Links section.
%Y Cf. A289815, A289816.
%K sign,tabl,base
%O 1,3
%A _Rémy Sigrist_, Jul 14 2017
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