349205domain: NAppears in sequencesNumber of peaks at odd level in all Dyck paths of semilength n with no UUU's and no DDD's, (U=(1,1), D=(1,-1)). These Dyck paths are counted by the secondary structure numbers (A004148).at n=15A166292a(n) = n^4 - 3*n^3 + 9*n^2 - 7*n + 5 (n>=1).at n=24A304162