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A056907
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Numbers k such that 36*k^2 + 12*k + 5 is prime (sorted by absolute values with negatives before positives).
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2
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0, -1, 1, 2, -3, -6, 6, -8, -11, 11, 12, 14, -16, 16, 17, 19, -21, -23, -26, 27, -28, 32, -34, -36, 36, -39, 39, -41, 42, 44, -46, 46, -48, -49, 51, 52, -53, -58, 62, 64, 67, -68, -71, 71, -76, 77, 79, 81, -84, -89, 91, 96, -99, -101, 101, 102, -104, -111, 111, -113
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OFFSET
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0,4
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COMMENTS
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36*k^2 + 12*k + 5 = (6*k+1)^2 + 4, which is four more than a square. Except for a(0), a(n) is never a multiple of 5.
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LINKS
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EXAMPLE
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a(3)=2 since 36*2^2 + 12*2 + 5 = 173 which is prime (as well as being four more than a square).
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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