A066303 Number of connected reduced partially ordered sets (posets) with n labeled elements.
1, 0, 6, 50, 1220, 42122, 2278248, 182111666, 21094774212, 3479970392642, 807001730170592, 260359119927269882, 115887302333840512956, 70677462143507496419690, 58725460618979611312258632
Offset: 1