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A177679
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Numbers k such that 30*k and 60*k are both the average of twin prime pairs.
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1
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1, 22, 27, 71, 85, 111, 113, 195, 209, 351, 1106, 1387, 1471, 1785, 1848, 1911, 2128, 2170, 2346, 2366, 2409, 2470, 2492, 2626, 2689, 2731, 2918, 3108, 3410, 3849, 4159, 4466, 4565, 5214, 5382, 5615, 6117, 6161, 6559, 7035, 7063, 7349, 7469, 7798, 7923
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(1)=1 because 30*1-1=29, 30*1+1=31, 60*1-1=59 and 60*1+1=61 are all twin primes.
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MATHEMATICA
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Select[Range[8000], AllTrue[{30#-1, 30#+1, 60#-1, 60#+1}, PrimeQ] &] (* Amiram Eldar, Dec 20 2019 *)
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PROG
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(Magma) [k:k in [1..8000]|IsPrime(30*k-1) and IsPrime(30*k+1) and IsPrime(60*k-1) and IsPrime(60*k+1)]; // Marius A. Burtea, Dec 20 2019
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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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Corrected (185 replaced by 195, 2718 replaced by 2918, 2731 inserted etc.) by R. J. Mathar, May 15 2010
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STATUS
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approved
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