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例子
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a(0)=2,因为2!=2 = 2^0 + 3^0.
a(1)=4,因为4!=24 = 11^1 + 13^1.
a(2)=8,因为8!=40320 = 2^2 + 3^2 + 5^2 + 7^2 + 11^2 + 13^2 + 17^2 + 19^2 + 23^2 + 29^2 + 41^2 + 59^2 + 181^2.
a(3)=10,因为10!=3628800 = 5^3 + 19^3 + 29^3 + 37^3 + 47^3 + 151^3.
a(4)=12,因为12!=479001600 = 3^4 + 5^4 + 7^4 + 11^4 + 17^4 + 19^4 + 29^4 + 31^4 + 37^4 + 47^4 + 53^4 + 59^4 + 73^4 + 79^4 + 97^4 + 131^4.
a(5)=15,因为15!=13^5 + 17^5 + 19^5 + 31^5 + 37^5 + 41^5 + 53^5 + 61^5 + 89^5 + 97^5 + 139^5 + 163^5 + 199^5 + 241^5.
a(6)=19,因为19!是中质数的6次幂之和{3, 7, 17, 23, 37, 43, 47, 53, 61, 71, 73, 79, 89, 101, 103, 107, 113, 127, 137, 157, 167, 193, 211, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463}.
a(7)=20,因为20!是{5,13,31,43,59,67,71,83,97,103,109,113,137,149,167,179,181,191,193,197,227,229,233,239,241,257,269,277,281,283,293,311,313,317,331}中素数的七次幂之和。
请注意,这些是可以进行这种表示的最小k。
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