75545domain: NAppears in sequencesNumber of Schur rings over Z_{3^n}.at n=9A270785a(n) = n^9 + 8*n^8 + 43*n^7 + 159*n^6 + 452*n^5 + 997*n^4 + 1725*n^3 + 2272*n^2 + 1990*n + 21.at n=2A270873Array T(n,k) of number of Schur rings over Z_{p^n} where n>=1 for p odd and k-th prime (by descending antidiagonals).at n=44A320948