Number of non-derangements of length n with 2 excedances.

Terms

a(0) =0a(1) =4a(2) =45a(3) =251a(4) =1078a(5) =4054a(6) =14115a(7) =46837a(8) =150612a(9) =474200a(10) =1471561a(11) =4520959a(12) =13792002a(13) =41867242a(14) =126649983a(15) =382177817a(16) =1151251648a(17) =3463715980a(18) =10412118981a(19) =31280396611a(20) =93933463950a(21) =281993329214a(22) =846382640155