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A078883
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Lesser member p of a twin prime pair such that p+1 is 3-smooth.
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6
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3, 5, 11, 17, 71, 107, 191, 431, 1151, 2591, 139967, 472391, 786431, 995327, 57395627, 63700991, 169869311, 4076863487, 10871635967, 2348273369087, 56358560858111, 79164837199871, 84537841287167, 150289495621631, 578415690713087, 1141260857376767
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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A000040(20) = 71 and 71+1 = 72 = 2^3*3^2 = A003586(17) and 71+2 = 73 = A000040(21), therefore 71 is a term.
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MATHEMATICA
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seq[max_] := Select[Sort[Flatten[Table[2^i*3^j - 1, {i, 1, Floor[Log2[max]]}, {j, 0, Floor[Log[3, max/2^i]]}]]], And @@ PrimeQ[# + {0, 2}] &]; seq[2*10^15] (* Amiram Eldar, Aug 27 2024 *)
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CROSSREFS
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Apart from initial terms, same as A059960.
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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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