Paradigmas_prolog_lr3

%task 1 default
summ(0,0).

summ(N,X):- N1 is N-1, summ(N1,X1), X is X1 + (4*N-1).

%task 1 tail

tail(0,T,T).
tail(N,T,R):- N1 is N - 1, T1 is T + (4*N-1),tail(N1,T1,R).

%task 2

f(0,1).
f(1,2).
f(N,R):-
N1 is N - 1,
N2 is N - 2,
f(N1,R1),
f(N2,R2),
R is R1 - 2 * R2.