212987263960domain: NAppears in sequencesNumber of permutations i_0,i_1,...,i_n of 0,1,...,n with i_0 = 0 and i_n = n, and with i_0+i_1, i_1+i_2, ..., i_{n-1}+i_n, i_n+i_0 all coprime to both n-1 and n+1.at n=19A228886