Number of involutions in the symmetric group S_n with at least one fixed point.

A378100

Number of involutions in the symmetric group S_n with at least one fixed point.

Terms

    a(0) =0a(1) =1a(2) =1a(3) =4a(4) =7a(5) =26a(6) =61a(7) =232a(8) =659a(9) =2620a(10) =8551a(11) =35696a(12) =129757a(13) =568504a(14) =2255345a(15) =10349536a(16) =44179711a(17) =211799312a(18) =962854399a(19) =4809701440a(20) =23103935021a(21) =119952692896a(22) =605135328337

External references