Factorial numbers written backwards.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =42a(5) =21a(6) =27a(7) =405a(8) =2304a(9) =88263a(10) =88263a(11) =861993a(12) =6100974a(13) =80207226a(14) =219287178a(15) =8634767031a(16) =88898722902a(17) =690824786553