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OFFSET
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1,1
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COMMENT
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A subset of A100349. No others < 10^9; conjecture that this sequence is finite.
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EXAMPLE
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4311-2=31*139, 4311-4=59*73, 4311-8=13*331, 4311-16=5*859, 4311-32=11*389, 4311-64=31*137, 4311-128=47*89, 4311-256=5*811, 4311-512=29*131, 4311-1024=19*173, 4311-2048=31*73, 4311-4096=5*43
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MATHEMATICA
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SemiPrimeQ[n_Integer] := If[Abs[n]<2, False, (2==Plus@@Transpose[FactorInteger[Abs[n]]][[2]])]; lst={}; Do[k=1; While[p=n-2^k; p>0 && SemiPrimeQ[p], k++ ]; If[p<=0, AppendTo[lst, n]], {n, 3, 1000000}]; lst
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CROSSREFS
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Cf. A039669 (n such that n-2^k is prime), A100349 (n such that n-2^k is prime or semiprime), A100350 (primes p such that p-2^k is prime or semiprime).
Sequence in context: A060760 A159368 A167065 this_sequence A045478 A055319 A029736
Adjacent sequences: A100348 A100349 A100350 this_sequence A100352 A100353 A100354
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KEYWORD
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bref,more,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Nov 18 2004
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