偶数分拆为 2 个素数之和, 这里有个绝对正确的公式。
Table[Length[Select[2 n - Prime[Range[PrimePi[n]]], PrimeQ]], {n, 2, 202}]
a(04)=1,
a(06)=1,
a(08)=1,
a(10)=2,
a(12)=1,
a(14)=2,
a(16)=2,
a(18)=2,
a(20)=2,
a(22)=2,
得到一串数:
1, 1, 1, 2, 1, 2, 2, 2, 2, 3, 3, 3, 2, 3, 2, 4, 4, 2, 3, 4, 3, 4, 5, 4, 3, 5, 3, 4, 6, 3, 5, 6, 2, 5, 6,
5, 5, 7, 4, 5, 8, 5, 4, 9, 4, 5, 7, 3, 6, 8, 5, 6, 8, 6, 7, 10, 6, 6, 12, 4, 5, 10, 3, 7, 9, 6, 5, 8, 7,
8, 11, 6, 5, 12, 4, 8, 11, 5, 8, 10, 5, 6, 13, 9, 6, 11, 7, 7, 14, 6, 8, 13, 5, 8, 11, 7, 9, 13, 8, 9,
14, 7, 7, 19, 6, 8, 13, 7, 9, 11, 7, 7, 12, 9, 7, 15, 9, 9, 18, 8, 9, 16, 6, 9, 16, 9, 8, 14, 10, 9,....
譬如:a(20230224)=129066
具体参考《整数序列在线百科全书(OEIS)》A045917
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