Formulae for solving Recurrences


Inductive Equation T(n)
T(n) = T(n-1) + bnk O(nk+1)
T(n) = cT(n-1) + bnk, for c > 1 O(cn)
T(n) = cT(n-1) + bdn, for c > 1 and c > d O(cn)
T(n) = cT(n-1) + bdn, for c > 1 and d > c O(dn)
T(n) = cT(n-1) + bdn, for c > 1 and c = d O(ncn)
T(n) = aT(n/b) + f(n), for f(n) < nlogb a O(nlogb a)
T(n) = aT(n/b) + f(n), for f(n) = nlogb a.logk n (k ≥ 0) O(nlogb a.logk+1 n)
T(n) = aT(n/b) + f(n), for f(n) > nlogb a O(f(n))
 
Generating Function Expansion
(1-x)-1 1 + x + x2 + x3 + x4 + x5 + ...
(1-x)-2 1 + 2x + 3x2 + 4x3 + 5x4 + 6x5 + ...
2 * (1-x)-3 2 + 6x + 12x2 + 20x3 + 30x4 + 42x5 + ...
(1-x)-3 1 + 3x + 6x2 + 10x3 + 15x4 + 21x5 + ...
(1-x)-4 1 + 4x + 10x2 + 20x3 + 35x4 + 56x5 + ...
(1-2x)-1 1 + 2x + 4x2 + 8x3 + 16x4 + 32x5 + ...
(1-3x)-1 1 + 3x + 9x2 + 27x3 + 81x4 + 243x5 + ...
(1-x2)-1 1 + x2 + x4 + x6 + x8 + x10 + ...
(1-x3)-1 1 + x3 + x6 + x9 + x12 + x15 + ...
(1-2x2)-1 1 + 2x2 + 4x4 + 8x6 + 16x8 + 32x10 + ...