A275541 (n)! + (n + 1)!!/(n + 1) - 2.

0, 0, 1, 6, 25, 126, 733, 5086, 40423, 363262, 3629743, 39920638, 479011993, 6227066878, 87178426333, 1307675013118, 20922791915023, 355687438417918, 6402373740187423, 121645100594626558, 2432902008831369073

Offset: 0

Author

Olivier Gérard, Aug 01 2016

Keywords

• nonn
• easy

Crossrefs

Cf. A006882, A128882.