A248832 The sum of denominators of unreduced mediants in Farey sequences of orders 1,2,..,n.

2, 6, 16, 34, 72, 122, 214, 338, 516, 734, 1062, 1438, 1970, 2586, 3322, 4186, 5322, 6566, 8152, 9898, 11896, 14114, 16838, 20254, 23982, 28196, 32746, 38108, 43710, 50242, 57286, 64990, 73238, 82326, 91846, 102698, 114234, 126706, 139818

Offset

0,1

Links

Table of n, a(n) for n=0..38.

Wikipedia, Mediant.

Wikipedia, Farey Sequence.

Formula

a(n) = 2*Sum_{k= 1,2,3,4..n} A213544(k).

Example

For n=4, the unreduced mediants are 1/2, 2/4, 5/10, 9/18, hence the sum of denominators is 2+4+10+18 = 34.

Crossrefs

Cf. A007306, A006843.

Sequence in context: A309691 A235792 A192706 * A280400 A199477 A330884

Adjacent sequences: A248829 A248830 A248831 * A248833 A248834 A248835

Keyword

nonn,easy

Author

Nehul Yadav, Oct 15 2014

Status

approved