Main diagonal of A139755, the table of q-derangement numbers of type A.

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =24a(5) =86a(6) =313a(7) =1157a(8) =4325a(9) =16303a(10) =61856a(11) =235917a(12) =903620a(13) =3473381a(14) =13391280a(15) =51761781a(16) =200523644a(17) =778342906a(18) =3026400508a(19) =11785538461a(20) =45959004812a(21) =179444813270a(22) =701422450293