%I #7 Aug 12 2021 18:36:33
%S 1,2,0,3,3,0,4,0,4,0,5,5,5,5,0,6,0,0,0,6,0,7,7,7,7,7,7,0,8,0,8,0,8,0,
%T 8,0,9,9,0,9,9,0,9,9,0,10,0,10,0,0,0,10,0,10,0
%N Triangle T(n,k) = n if gcd(n,k)=1, =0 otherwise.
%F T(n,k) = n *A054521(n,k), 1<=k<=n.
%e First few rows of the triangle are:
%e 1;
%e 2, 0;
%e 3, 3, 0;
%e 4, 0, 4, 0;
%e 5, 5, 5, 5, 0;
%e 6, 0, 0, 0, 6, 0;
%e 7, 7, 7, 7, 7, 7, 0;
%e ...
%t Table[If[GCD[n,k]==1,n,0],{n,10},{k,n}]//Flatten (* _Harvey P. Dale_, Aug 12 2021 *)
%Y Cf. A002618 (row sums), A054521.
%K nonn,tabl,easy
%O 1,2
%A _Gary W. Adamson_, Jan 14 2007