A126577 a(n) = numerator of the sum of reciprocals of the terms in n-th row of triangle A077581.
1, 4, 7, 176, 9, 133542, 103, 91072, 99527, 131023748, 7591, 300996993816, 88001, 1403843964196, 44094737, 10686452707072, 825533, 368070779365071896502, 2895701, 8653175044141052500, 81659533540907, 3080940707518158404
Offset: 1
Examples
Row 4 of triangle A077581 is (1,3,5,7). So a(4) is the numerator of 1/1 +1/3 +1/5 + 1/7 = 176/105.
Programs
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Mathematica
row[n_] := Take[Select[Range[n^2], GCD[ #, n] == 1 &], n]; Table[Numerator[Plus @@ (1/# &) /@ row[n]], {n, 23}] (* Ray Chandler, Dec 29 2006 *)
Extensions
Extended by Ray Chandler, Dec 29 2006