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A327240
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3-smooth numbers k such that k-1 and (k-2)/2 are prime.
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3
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6, 8, 12, 24, 48, 108, 384, 864, 8748, 995328, 2348273369088, 7421703487488, 21422803359744, 3470494144278528, 161919374795459002368, 1838129271989302091317248, 2168345519443636233418208968704, 28070062609828769223367060340342784
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OFFSET
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1,1
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COMMENTS
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Numbers k of the form 2^a*3^b such that k-1 and (k-2)/2 are prime.
For all terms k except 6 and 8, k-2 is in A325204.
All terms except 6 and 12 end in 4 or 8.
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LINKS
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EXAMPLE
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a(3)=12 is a term because 12=2^2*3 and 11 and 10/2 are prime.
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MATHEMATICA
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nmax = 10^35;
Select[Sort[Flatten[Table[2^i*3^j, {j, 0, Log[3, nmax]}, {i, Log[2, nmax/3^j]}]]], PrimeQ[# - 1] && PrimeQ[(# - 2)/2] &]
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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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