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A135976
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Mersenne composites (A065341) with exactly 2 prime factors.
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7
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2047, 8388607, 137438953471, 2199023255551, 576460752303423487, 147573952589676412927, 9671406556917033397649407, 158456325028528675187087900671, 2535301200456458802993406410751
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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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MAPLE
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i := 2^(ithprime(n))-1:
if (nops(numtheory[factorset](i)) = 2) then
RETURN (i)
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MATHEMATICA
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k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], c = FactorInteger[2^Prime[n] - 1]; d = Length[c]; If[d == 2, AppendTo[k, 2^Prime[n] - 1]]], {n, 1, 40}]; k
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PROG
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(PARI) forprime(p=1, 1e2, if(bigomega(2^p-1)==2, print1(2^p-1, ", "))) \\ Felix Fröhlich, Aug 12 2014
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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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