Question

Write this recursive function in Pascal and test it with small values of ’n’: F0 = F1 = F2 = 1

if n is even: Fn = nFn−1 + (n − 1)Fn−2 + (n − 2)Fn−3

if n is odd: Fn = (n − 2)Fn−1 + (n − 1)Fn−2 + nFn−3

Answer 1

Code

program recursion;

var
(* local variable declaration *)
n: integer;
result: integer;
  
(*function definition *)
function test (n: integer): integer;
var
(* local variable declaration *)
result: integer;

begin
if((n=0) or (n=1) or (n=2)) then
Exit(1);
  
if(n mod 2 = 0) then
result := n*test(n-1) + (n-1)*test(n-2) + (n-2)*test(n-3)
else
result := (n-2)*test(n-1) + (n-1)*test(n-2) + n*test(n-3);
  
Exit(result);
  
end;
  
begin
n := 6;
result := test(n);
writeln(result)
end.

Test Output

For n=6

For n=5