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

Author

Nehul Yadav, Oct 15 2014

Keywords

• nonn
• easy

Examples

			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.
		

Links

• Wikipedia, Mediant.
• Wikipedia, Farey Sequence.

Crossrefs

Cf. A007306, A006843.

Formula

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