A272042 a(n) = 2*prime(2n) - prime(n).

4, 11, 21, 31, 47, 61, 69, 87, 99, 113, 127, 141, 161, 171, 179, 209, 219, 241, 259, 275, 289, 307, 315, 357, 361, 377, 399, 419, 433, 449, 459, 491, 497, 535, 549, 567, 589, 603, 627, 645, 663, 685, 695, 721, 729

Offset: 1

Author

Andres Cicuttin, Apr 18 2016

Keywords

• nonn
• easy

Examples

			For n=1, 2*prime(2*1)-prime(1) = 2*3 - 2 = 4.
For n=10, 2*prime(2*10)-prime(10) = 2*71 - 29 = 113.
		

Programs

Mathematica

Table[2*Prime[2 n] - Prime[n], {n, 1, 45}]

PARI

a(n) = 2*prime(2*n) - prime(n) \\ Charles R Greathouse IV, Apr 18 2016

Formula

a(n) = 3n*log n + 3n*log log n - (3-log 2)*n + O(n log log n/log n). - Charles R Greathouse IV, Apr 18 2016

a(n) = A072473(n) + A031215(n). - R. J. Mathar, Apr 20 2016