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 A099611 a(n) is the largest odd number that is less than n^2 and is the product of two distinct primes. 3
 15, 21, 35, 39, 57, 77, 95, 119, 143, 161, 187, 221, 253, 287, 323, 355, 395, 437, 481, 527, 573, 623, 671, 723, 781, 835, 899, 959, 1011, 1081, 1149, 1219, 1293, 1363, 1441, 1517, 1591, 1679, 1763, 1843, 1929, 2021, 2105, 2201, 2291, 2395, 2497, 2599, 2701 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,1 COMMENTS a(n) < A000290(n) < A099610(n); subsequence of A046388. The offset is 4 since a(n) does not exist for n <= 3. LINKS Table of n, a(n) for n=4..52. MATHEMATICA Module[{nn=70, p2p}, p2p=Reverse[Union[Times@@@Subsets[Prime[Range[ 2, PrimePi[ Ceiling[ nn^2/3]]]], {2}]]]; Table[SelectFirst[p2p, #

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Last modified February 23 18:28 EST 2024. Contains 370283 sequences. (Running on oeis4.)