#fib(n): then nth Fibonacci number
fib:=proc(n) option remember: 

if n<=0 then
 1:
elif n=1 then
 2:
else
 fib(n-1)+fib(n-2):
fi:   


end:

#fib1(n): then nth Fibonacci number
fib1:=proc(n) option remember: 

if n<=0 then
 1:
elif n=1 then
 3:
else
 fib1(n-1)+fib1(n-2):
fi:
   



end:


#fib2(n): then nth Fibonacci number
fib2:=proc(n) option remember: 

if n<=0 then
 1:
elif n=1 then
 1:
else
 (n+1)*fib2(n-1)+(n^2-1)*fib2(n-2):
fi:
   



end: