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A375182

Slowest increasing sequence of semiprimes such that the differences of successive terms are distinct.

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

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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

Robert Israel, Table of n, a(n) for n = 1..10000

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