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A280708
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Lexicographically earliest sequence such that no subsequence sums to a prime.
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1
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1, 8, 24, 24, 86, 1260, 1890, 14136, 197400, 10467660, 1231572090
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OFFSET
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1,2
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COMMENTS
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This sequence is monotonically increasing.
So far, apart from a(4) this sequence is identical to A052349.
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LINKS
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EXAMPLE
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For n = 4, a(4) = 24 because all subsets have nonprime sums:
1 + 8 = 9 = 3^2
1 + 24 = 25 = 5^2
8 + 24 = 32 = 2^5
24 + 24 = 48 = 2^4*3
1 + 8 + 24 = 33 = 3*11
1 + 24 + 24 = 49 = 7^2
8 + 24 + 24 = 56 = 2^3*7
1 + 8 + 24 + 24 = 57 = 3*19
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MAPLE
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S:= {0}: count:= 0:
x:= 1:
while x < 10^6 do
if ormap(s -> isprime(s+x), S) then x:= x+1
else
count:= count+1;
A[count]:= x;
S:= S union map(`+`, S, x);
fi
od:
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MATHEMATICA
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t = {1}; c = 1; Print[1]; While[Length[t] < 11, r = Rest[Subsets[t]]; s = Table[Total[r[[i]]], {i, Length[r]}]; While[PrimeQ[c] || Union[PrimeQ[s + c]] != {False}, c++]; Print[c]; AppendTo[t, c]] (* Hans Havermann, Jan 20 2017 *)
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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