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A375182
Slowest increasing sequence of semiprimes such that the differences of successive terms are distinct.
1
4, 6, 9, 10, 14, 21, 26, 34, 46, 55, 65, 82, 93, 106, 121, 141, 155, 161, 177, 201, 219, 247, 274, 295, 314, 339, 361, 391, 417, 446, 469, 501, 535, 566, 611, 649, 685, 718, 753, 793, 835, 878, 917, 958, 995, 1041, 1094, 1138, 1186, 1238, 1285, 1339, 1389, 1438, 1497, 1555, 1618, 1673, 1735, 1795, 1851
OFFSET
1,1
COMMENTS
For n >= 2, a(n) is the least semiprime k > a(n-1) such that k - a(n-1) <> a(j) - a(j-1) for j < n.
LINKS
MAPLE
R:= 4: x:= 4: S:= {}: count:= 1:
for i from 6 while count < 100 do
if not member(i-x, S) and numtheory:-bigomega(i) = 2 then
R:= R, i; S:= S union {i-x}; x:= i; count:= count+1
fi
od:
R;
MATHEMATICA
s = {4, 6}; df = {2}; Do[k = 1; While [MemberQ[df, k] ||
2 != PrimeOmega[a = s[[-1]] + k], k++]; AppendTo[s, a]; AppendTo[df, k], {98}];
s
CROSSREFS
Sequence in context: A054395 A142863 A318990 * A132435 A108631 A200677
KEYWORD
nonn
AUTHOR
Zak Seidov and Robert Israel, Sep 23 2024
STATUS
approved