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 A280708 Lexicographically earliest sequence such that no subsequence sums to a prime. 1
 1, 8, 24, 24, 86, 1260, 1890, 14136, 197400, 10467660, 1231572090 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence is monotonically increasing. So far, apart from a(4) this sequence is identical to A052349. LINKS EXAMPLE 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 MAPLE 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: seq(A[i], i=1..count); # Robert Israel, Jan 20 2017 MATHEMATICA t = {1}; c = 1; Print; 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 *) CROSSREFS Cf. A052349. Sequence in context: A088448 A005878 A128637 * A109272 A052349 A254448 Adjacent sequences:  A280705 A280706 A280707 * A280709 A280710 A280711 KEYWORD nonn,hard,more AUTHOR Peter Kagey, Jan 07 2017 EXTENSIONS a(9) and a(10) from Dmitry Kamenetsky, Jan 12 2017 a(11) from Hans Havermann, Jan 20 2017 STATUS approved

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Last modified August 7 06:02 EDT 2020. Contains 336274 sequences. (Running on oeis4.)