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A067189
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Numbers that can be expressed as the sum of two primes in exactly three ways.
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12
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22, 24, 26, 30, 40, 44, 52, 56, 62, 98, 128
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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26 is a term as 26 = 23+3 = 19+7 = 13+13 are all the three ways to express 26 as a sum of two primes.
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CROSSREFS
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Numbers that can be expressed as the sum of two primes in k ways for k=0..10: A014092 (k=0), A067187 (k=1), A067188 (k=2), this sequence (k=3), A067190 (k=4), A067191 (k=5), A066722 (k=6), A352229 (k=7), A352230 (k=8), A352231 (k=9), A352233 (k=10).
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KEYWORD
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nonn,fini,full
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AUTHOR
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EXTENSIONS
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Extended by Peter Bertok (peter(AT)bertok.com), who finds (Jan 13 2002) that there are no other terms below 10000 and conjectures there are no further terms in this sequence and A067188, A067190, etc.
R. K. Guy (Jan 14 2002) remarks: "I believe that these conjectures follow from a more general one by Hardy & Littlewood (probably in Some problems of 'partitio numerorum' III, on the expression of a number as a sum of primes, Acta Math. 44(1922) 1-70)."
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STATUS
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approved
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