集合{Ø, a, {a} }的幂集是:
A. { {Ø}, {a}, {{a}} }
B. { {a}, {{a}}, {a,{a}} }
C. {Ø, {a}, {{a}}, {Ø,a}, {Ø, {a}}, {a,{a}}, {Ø,a, {a}} }
D. {Ø, {Ø}, {a}, {{a}}, {Ø,a}, {Ø, {a}}, {a,{a}}, {Ø,a, {a}} }
给出序列an=3an-1+2an-2+an-3,n=3,4,5…,a0=2,a1=3,a2=4的递归求解算法解:procedure sequence(n : nonnegative integer)if n < 3 then return n + 2else return _______________
A. sequence(n - 1) + sequence(n - 2) + sequence(n - 3)
B. 3*sequence(n - 1) + 2*sequence(n - 2) + sequence(n - 3)
C. sequence(n - 1) + 2*sequence(n - 2) + 3*sequence(n - 3)
D. 3*sequence(n - 1) + 2*sequence(n - 2) + sequence(n - 3) + 2