A188225 Number of ways to select 15 knights from n knights sitting at a round table if no adjacent knights are chosen.

2, 31, 256, 1496, 6936, 27132, 93024, 286824, 810084, 2124694, 5230016, 12183560, 27041560, 57500460, 117675360, 232676280, 445962870, 830905245, 1508593920, 2674776720, 4639918800, 7887861960, 13160496960, 21578373360, 34810394760

Offset: 30

Author

Zoltán Lőrincz, Mar 30 2011

Keywords

• nonn

Examples

			For n = 30 a(30) = C(15, 15) + C(14, 14) = 2
		

Crossrefs

a(n) = A010968(n - 15) + A010967(n - 16)

Programs

Mathematica

Table[Binomial[n-15,15]+Binomial[n-16,14],{n,30,60}] (* Harvey P. Dale, May 16 2018 *)

Formula

a(n) = C(n - 15, 15) + C(n - 16, 14)