Strehl's sequence "C_n^(3)".A000658Strehl's sequence "C_n^(3)".Terms a(0) =1a(1) =4a(2) =68a(3) =1732a(4) =51076a(5) =1657904a(6) =57793316a(7) =2117525792a(8) =80483121028External referencesoeis: A000658