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楼主 |
发表于 2023-6-19 21:17
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谢谢 yangchuanju 提供,
A099410
Numbers k such that 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
0, 2, 3, 5, 14, 176, 416, 2505, 2759, 7925, 9401, 10391, 12105, 19616
22229|2w9 |(2*10^n+61)/9 |n=2,3,5,14,176,416,2505,2759,7925,9401,10391,12105,19616,261704,264539
A098089
Numbers k such that 7*R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
0, 2, 66, 86, 90, 102, 386, 624, 7784, 18536, 113757, 135879
77779|7w9 |(7*10^n+11)/9 |n=2,66,86,90,102,386,624,7784,18536,113757,135879
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