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A172296
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Partial sums of Wagstaff numbers A000978.
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0
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3, 8, 15, 26, 39, 56, 75, 98, 129, 172, 233, 312, 413, 540, 707, 898, 1097, 1410, 1757, 2458, 4167, 6784, 10323, 16130, 26631, 37322, 48601, 60992, 75471, 118208, 201547, 296916, 414155, 541186, 680123, 821202, 1088219, 1358206, 1732527, 2718718
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OFFSET
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1,1
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COMMENTS
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The prime partial sums of Wagstaff numbers begin 3, 233, 1097, 201547, 680123. None of these but 3 is itself a Wagstaff number.
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LINKS
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FORMULA
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a(n) = SUM[i=1..n] {integers i such that (2^i + 1)/3 is prime}.
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EXAMPLE
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a(40) = 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 31 + 43 + 61 + 79 + 101 + 127 + 167 + 191 + 199 + 313 + 347 + 701 + 1709 + 2617 + 3539 + 5807 + 10501 + 10691 + 11279 + 12391 + 14479 + 42737 + 83339 + 95369 + 117239 + 127031 + 138937 + 141079 + 267017 + 269987 + 374321 + 986191.
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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STATUS
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approved
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