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A087338
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a(1) = 1, then the smallest number > 1 such that both every partial sum and every partial product + 1 are prime for n > 1.
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1
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1, 2, 2, 18, 6, 8, 30, 4, 26, 6, 6, 4, 50, 4, 56, 6, 22, 6, 50, 40, 12, 24, 138, 20, 132, 70, 78, 8, 232, 2, 160, 144, 32, 322, 12, 44, 216, 294, 60, 394, 1460, 82, 54, 452, 168, 1024, 86, 76, 308, 208, 104, 456, 268, 396, 350, 120, 10, 236, 180, 402, 112, 336, 530, 318, 112
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Partial sums: 1+2 = 3, 1+2+2 = 5, 1+2+2+18 = 23;
partial products + 1: 1*2 + 1 = 3, 1*2*2 + 1 = 5, 1*2*2*18 + 1 = 73.
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MATHEMATICA
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a = {1}; s = 1; p = 1; Do[k = 2; While[ !PrimeQ[s + k] || !PrimeQ[p*k + 1], k++ ]; AppendTo[a, k]; s += k; p *= k, {n, 1, 65}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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