A126578 a(n) = denominator of the sum of reciprocals of the terms in n-th row of triangle A077581.

1, 3, 4, 105, 4, 85085, 40, 45045, 40040, 66927861, 2520, 167133741775, 27720, 644658718275, 16997552, 4512611027925, 240240, 190103424450275260925, 816816, 3873805630307495883, 28269478608800, 1257729100749186975, 15519504

Offset

1,2

Links

Table of n, a(n) for n=1..23.

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

Cf. A077581, A126577.

Sequence in context: A041253 A297119 A156182 * A332972 A041351 A266516

Adjacent sequences: A126575 A126576 A126577 * A126579 A126580 A126581

Keyword

frac,nonn

Author

Leroy Quet, Dec 28 2006

Extensions

Extended by Ray Chandler, Dec 29 2006

Status

approved