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A117499
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Number of subsets of {n-1, n, n+1} that sum up to a prime.
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4
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4, 4, 4, 3, 2, 4, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 1, 3, 2, 2, 2, 2, 2, 2, 0, 1, 1, 1, 2, 4, 2, 1, 1, 1, 1, 3, 2, 1, 1, 2, 2, 3, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 2, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 1, 0, 2, 2, 1, 1, 2, 2, 2, 0, 1, 1, 1, 2, 3, 1, 0, 0, 0, 1, 3, 2, 2, 2, 2, 1, 2, 1, 1, 1
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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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FORMULA
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EXAMPLE
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a(1) = #{2, 0+2=2, 1+2=3, 0+1+2=3} = 4;
a(2) = #{2, 3, 1+2=3, 2+3=5} = 4;
a(3) = #{2, 3, 2+3=5, 3+4=7} = 4;
a(4) = #{3, 5, 3+4=7} = 3;
a(5) = #{5, 5+6=11} = 2.
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MATHEMATICA
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Table[Length[Select[{-1+n, n, 1+n, -1+2 n, 2 n, 1+2 n, 3 n}, PrimeQ]], {n, 105}]
ssp[{a_, b_, c_}]:=Count[Subsets[{a, b, c}, 3], _?(PrimeQ[Total[#]]&)]; ssp/@ Partition[ Range[0, 110], 3, 1] (* Harvey P. Dale, Jan 29 2013 *)
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PROG
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(Haskell)
a117499 1 = sum $ map a010051 [1, 2, 0 + 1, 0 + 2, 1 + 2, 0 + 1 + 2]
a117499 n = sum $ map a010051 [n - 1, n, n + 1, 2 * n - 1, 2 * n + 1]
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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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