Number of undirected circular permutations i_0, i_1, ..., i_n of 0, 1, ..., n such that all the 2*n+2 numbers |i_0 +/- i_1|, |i_1 +/- i_2|, ..., |i_{n-1} +/- i_n|, |i_n +/- i_0| have the form (p-1)/2 with p an odd prime.
A228956
Number of undirected circular permutations i_0, i_1, ..., i_n of 0, 1, ..., n such that all the 2*n+2 numbers |i_0 +/- i_1|, |i_1 +/- i_2|, ..., |i_{n-1} +/- i_n|, |i_n +/- i_0| have the form (p-1)/2 with p an odd prime.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =9a(6) =17a(7) =84a(8) =30a(9) =127a(10) =791a(11) =2404a(12) =11454a(13) =27680a(14) =25942a(15) =137272a(16) =515947a(17) =2834056a(18) =26583034a(19) =82099932a(20) =306004652a(21) =4518630225a(22) =11242369312a(23) =8942966426a(24) =95473633156a(25) =533328765065
External references
- oeis: A228956