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A172255
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Partial sums of the Fermat pseudoprimes to base 2, A001567.
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1
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341, 902, 1547, 2652, 4039, 5768, 7673, 9720, 12185, 14886, 17707, 20984, 25017, 29386, 33757, 38438, 43899, 50500, 58457, 66778, 75259, 84170, 94431, 105016, 116321, 129122, 142863, 156610, 170591, 185082, 200791, 216632, 233337, 252042
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OFFSET
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1,1
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COMMENTS
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The subsequence of pseudoprimes in this sequence begins 341; the next term exceeds a(10000) if it exists. - Charles R Greathouse IV, Aug 22 2012
The subsequence of primes in the sequence begins 7673, 17707, 33757, 270763, 484621.
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LINKS
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FORMULA
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a(n) = SUM[i=1..n] {odd composite numbers n such that 2^(n-1) == 1 mod n}.
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EXAMPLE
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a(15) = 341 + 561 + 645 + 1105 + 1387 + 1729 + 1905 + 2047 + 2465 + 2701 + 2821 + 3277 + 4033 + 4369 + 4371 = 33757 is prime.
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PROG
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(PARI) sums(v)=my(s); vector(#v, i, s+=v[i])
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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