OFFSET
1,2
EXAMPLE
Row 4 of triangle A077581 is (1,3,5,7).
So a(4) is the denominator of 1/1 +1/3 +1/5 + 1/7 = 176/105.
MATHEMATICA
row[n_] := Take[Select[Range[n^2], GCD[ #, n] == 1 &], n]; Table[Denominator[Plus @@ (1/# &) /@ row[n]], {n, 23}] (* Ray Chandler, Dec 29 2006 *)
CROSSREFS
KEYWORD
frac,nonn
AUTHOR
Leroy Quet, Dec 28 2006
EXTENSIONS
Extended by Ray Chandler, Dec 29 2006
STATUS
approved