A291286 a(0)=1, a(1)=2, thereafter a(n) = n*a(n-1)+(n-1)*(n-2)*a(n-2).
1, 2, 4, 16, 88, 632, 5552, 57824, 695776, 9500128, 145097152, 2451080192, 45373649024, 913400022656, 19865889564928, 464227147597312, 11599471170191872, 308605525316616704, 8709955613991289856, 259922447412719218688, 8177253768239405504512
Offset: 0
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Programs
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Maple
f:=proc(n) option remember; if n <= 1 then n+1 else n*f(n-1)+(n-1)*(n-2)*f(n-2); fi; end; [seq(f(n),n=0..40)];