A024850 Let c(k) denote the k-th composite number and p(k) the k-th prime number; then a(n) = Sum_{i=n*(n-1)/2+1 .. n*(n+1)/2} c(i) - Sum_{i=1..n} p(i).

2, 9, 21, 46, 84, 135, 206, 308, 429, 583, 772, 987, 1265, 1552, 1906, 2308, 2767, 3278, 3840, 4478, 5201, 5956, 6783, 7704, 8706, 9777, 10976, 12241, 13591, 14985, 16546, 18230, 20019, 21862, 23824, 25907, 28111, 30474, 32897, 35482, 38208, 41125, 44159, 47239, 50516, 53944

Offset: 1

Author

Amarnath Murthy and Benoit Cloitre, Jun 23 2002

Keywords

• nonn

Examples

			a(1) = 4 - 2 = 2.
a(2) = 6 + 8 - 2 - 3 = 9.
a(3) = 9 + 10 + 12 - 2 - 3 - 5 = 21.
		

Crossrefs

Cf. A071411.

Formula

a(n) = A072475(n) - A007504(n) [corrected by Sean A. Irvine, Jul 26 2019].

Extensions

a(7) and a(8) corrected and more terms from Sean A. Irvine, Jul 26 2019