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A026433
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a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n.
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2
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2, 3, 4, 6, 8, 9, 10, 12, 13, 14, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 44, 45, 46, 48, 49, 50, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94, 96
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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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MAPLE
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N:= 1000: # to get all terms <= N
V:= Vector(N):
a[1]:= 2: finished:= false:
for n from 2 do
for i from a[n-1]+1 do
if i > N then
finished:= true; break
elif V[i] = 0 then break
fi
od:
if finished then break fi;
a[n]:= i;
S:= select(`<=`, [seq(a[j]*i-1, j=1..n-1)], N);
if S <> [] then V[S]:= 1 fi;
od:
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MATHEMATICA
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a = {2, 3}; used = {a[[1]]*a[[2]] - 1}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a - 1]; AppendTo[a, k], {n, 3, 60}]; a (* Ivan Neretin, Mar 06 2016 *)
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CROSSREFS
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Cf. A026431 and references therein.
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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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