Number of singly defective permutations of 1..n with exactly 1 maximum.

Terms

a(0) =0a(1) =2a(2) =15a(3) =64a(4) =220a(5) =672a(6) =1904a(7) =5120a(8) =13248a(9) =33280a(10) =81664a(11) =196608a(12) =465920a(13) =1089536a(14) =2519040a(15) =5767168a(16) =13090816a(17) =29491200a(18) =65994752a(19) =146800640a(20) =324796416a(21) =715128832a(22) =1567621120a(23) =3422552064a(24) =7444889600a(25) =16139681792a(26) =34879832064a(27) =75161927680a(28) =161531035648a(29) =346281738240