A351357 Irregular triangle read by rows T(n,k): number of binary necklaces with n beads, k of them black, and at least three consecutive black beads.
0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 2, 1, 1, 0, 0, 0, 1, 3, 3, 1, 1, 0, 0, 0, 1, 4, 6, 4, 1, 1, 0, 0, 0, 1, 5, 10, 9, 4, 1, 1, 0, 0, 0, 1, 6, 15, 19, 12, 5, 1, 1, 0, 0, 0, 1, 7, 21, 33, 29, 15, 5, 1, 1, 0, 0, 0, 1, 8, 28, 54, 60, 42, 19, 6, 1, 1, 0, 0, 0, 1, 9, 36, 81, 111, 96, 55, 22, 6, 1, 1
Offset: 1
Examples
Triangle begins: 0, 0; 0, 0, 0; 0, 0, 0, 1; 0, 0, 0, 1, 1; 0, 0, 0, 1, 1, 1; 0, 0, 0, 1, 2, 1, 1; 0, 0, 0, 1, 3, 3, 1, 1; 0, 0, 0, 1, 4, 6, 4, 1, 1;
Links
- Marko R. Riedel et al., Necklaces made of black and white beads, Math StackExchange, Feb 2022.