a(n) = -Floor[n/2]! + Sum[(Eulerian[n - j, j]), {j, 0, Floor[n/2]}].

A174993

a(n) = -Floor[n/2]! + Sum[(Eulerian[n - j, j]), {j, 0, Floor[n/2]}].

Terms

    a(0) =0a(1) =0a(2) =1a(3) =4a(4) =11a(5) =36a(6) =119a(7) =443a(8) =1718a(9) =7245a(10) =32313a(11) =153730a(12) =771677a(13) =4088053a(14) =22741818a(15) =132596893a(16) =807840501a(17) =5132194862a(18) =33924901021a(19) =232905225561

External references