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A206041
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Values of the difference d for 7 primes in arithmetic progression with the minimal start sequence {7 + j*d}, j = 0 to 6.
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14
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150, 2760, 3450, 9150, 14190, 20040, 21240, 63600, 76710, 117420, 122340, 134250, 184470, 184620, 189690, 237060, 274830, 312000, 337530, 379410, 477630, 498900, 514740, 678750, 707850, 1014540, 1168530, 1180080, 1234530, 1251690, 1263480, 1523520, 1690590
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OFFSET
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1,1
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COMMENTS
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The computations were done without any assumptions on the form of d.
All terms are multiples of 30. - Zak Seidov, Jan 07 2014.
Equivalently, integers d such that the longest possible arithmetic progression (AP) of primes with common difference d has exactly 7 elements (see example). These 7 elements are not necessarily consecutive primes. In fact, for each term d, there exists only one such AP of primes, and this one always starts with A342309(d) = 7, so this unique AP is (7, 7+d, 7+2d, 7+3d, 7+4d, 7+5d, 7+6d). - Bernard Schott, Feb 12 2023
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LINKS
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Diophante, A1880. NP en PA (prime numbers in arithmetic progression) (in French).
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FORMULA
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EXAMPLE
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d = 150 then {7, 7 + 1*150, 7 + 2*150, 7 + 3*150, 7 + 4*150, 7 + 5*150, + 7 + 6*150} = {7, 157, 307, 457, 607, 757, 907} which is 7 primes in arithmetic progression.
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MAPLE
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filter := d -> isprime(7+d) and isprime(7+2*d) and isprime(7+3*d) and isprime(7+4*d) and isprime(7+5*d) and isprime(7+6*d): select(filter, [$(1 .. 1700000)]); # Bernard Schott, Feb 13 2023
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MATHEMATICA
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a = 7; t = {}; Do[If[PrimeQ[{a, a + d, a + 2*d, a + 3*d, a + 4*d, a + 5*d, a + 6*d}] == {True, True, True, True, True, True, True}, AppendTo[t, d]], {d, 200000}]; t
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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