var s,ss:integer; 
 function F( n: integer ): integer; 
 begin 
   if n < 4  then begin 
     Result := n-1; 
     Exit; 
   end; 
   if (n > 3) and (n mod 3=0)  then 
      Result :=n+ 2*F(n-1) 
   else 
      Result :=F(n-2)+F(n-3) 
 end; 
 begin 
   s := F(25); 
   ss:=0; 
   while s>0 do begin 
      ss := ss+s mod 10; 
      s := s div 10; 
   writeln( 'summa = ',ss ); 
   end; 
 end. 
 

  
 
 цитата:
m = {}  
  def F( n ):  
    if n in m:  
      return m[n]  
    if n == 0:  
      res = 1  
    elif n > 0:  
      res = 2*F(1-n) + 3*F(n-1) + 2  
    else:  
      res = -F(-n)  
    m[n] = res  
    return res  
    
  print( sum( map(int, str(F(5))) ) ) 

 

 
 def F( n ): 
   if n == 0: 
     res = 1 
   elif n > 0: 
     res = 2*F(1-n) + 3*F(n-1) + 2 
   else: 
     res = -F(-n) 
   return res 
  
 print(F(50)) 
 

 
 from functools import lru_cache  
 @lru_cache(None) 
  
 def F( n ): 
   if n == 0: 
     res = 1 
   elif n > 0: 
     res = 2*F(1-n) + 3*F(n-1) + 2 
   else: 
     res = -F(-n) 
   return res 
  
 s = F(50) 
 ss = 0 
 while s>0: 
    ss = ss+s%10; 
    s = s//10; 
  
 print(ss)