Number of undirected circular permutations i_0, i_1, ..., i_n of 0, 1, ..., n such that i_0+i_1, i_1+i_2, ...,i_{n-1}+i_n, i_n+i_0 are among those k with 6*k-1 and 6*k+1 twin primes.
A228917
Number of undirected circular permutations i_0, i_1, ..., i_n of 0, 1, ..., n such that i_0+i_1, i_1+i_2, ...,i_{n-1}+i_n, i_n+i_0 are among those k with 6*k-1 and 6*k+1 twin primes.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =2a(6) =5a(7) =2a(8) =12a(9) =39a(10) =98a(11) =526a(12) =2117a(13) =6663a(14) =15043a(15) =68403a(16) =791581a(17) =4826577a(18) =19592777a(19) =102551299a(20) =739788968a(21) =4449585790a(22) =36547266589a(23) =324446266072
External references
- oeis: A228917