A282517 Number of n-element subsets of [2n] having a prime element sum.

0, 1, 4, 6, 21, 59, 239, 760, 2970, 10060, 38930, 124735, 503767, 1986024, 7059818, 27806989, 107739266, 376458328, 1421570461, 5750402871, 23095812036, 89360066340, 315720338715, 1202284699132, 5133364318360, 20343420316531, 74430884941912, 279471388089807

Offset: 0

Author

Alois P. Heinz, Feb 17 2017

Keywords

• nonn

Examples

			a(1) = 1: {2}.
a(2) = 4: {1,2}, {1,4}, {2,3}, {3,4}.
a(3) = 6: {1,2,4}, {1,4,6}, {2,3,6}, {2,4,5}, {2,5,6}, {3,4,6}.
a(4) = 21: {1,2,3,5}, {1,2,3,7}, {1,2,4,6}, {1,2,6,8}, {1,3,4,5}, {1,3,5,8}, {1,3,6,7}, {1,3,7,8}, {1,4,5,7}, {1,4,6,8}, {1,5,6,7}, {2,3,4,8}, {2,3,5,7}, {2,3,6,8}, {2,4,5,6}, {2,4,5,8}, {2,4,6,7}, {2,6,7,8}, {3,4,5,7}, {3,5,7,8}, {4,5,6,8}.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..130

Crossrefs

Cf. A282516.

Formula

a(n) = A282516(2n,n).