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A133597
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Array of semiprimes, read by antidiagonals, where row k is the first of pairs of consecutive semiprimes j and j+k.
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0
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9, 4, 14, 35, 49, 21, 215, 46, 55, 25, 69, 299, 62, 91, 33, 15, 77, 1135, 74, 119, 34, 26, 123, 106, 1343, 82, 143, 38, 169, 39, 371, 161, 1835, 115, 159, 57, 146, 437, 134, 377, 178, 1891, 155, 183, 85, 237, 226, 458, 187, 505, 221, 1939, 166, 185, 86
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Every semiprime that occurs in this table occurs only once. The semiprimes which are not in this table (first 10 rows only) begin: 6, 10, 22, 51, 55, 58, 65, 87, ... leading to the question: which semiprimes occur nowhere in the complete table? Note that similar tables exist for k-almost primes (integers with exactly k prime factors, with multiplicity), this being the k=2 slice of a 3-dimensional array..
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EXAMPLE
| The array begins:
==================================================================
n=......1....2.....3....4....5....6....7....8....9...10
==================================================================
k=1.|...9...14....21...25...33...34...38...57...85...86....A070552
k=2.|...4...49....55...91..119..143..159..183..185..203....A136196
k=3.|..35...46....62...74...82..115..155..166..206..259....
k=4.|.215..299..1135.1343.1835.1891.1939.3095.3153.4411....
k=5.|..69...77...106..161..178..221..254..309..314..329....
k=6.|..15..123...371..377..505..511..545..573..591..649....
k=7.|..26...39...134..187..194..267..519..566..655..771....
k=8.|.169..437...458..614..723..737..905..965.1047.1059....
k=9.|.146..226...278..346.1018.1177.1273.1546.1594.1865....
k=10|.237..427..1027.1101.1661.2723.2747.3173.3295.3669....
==================================================================
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CROSSREFS
| Cf. A001358, A070552, A136196.
Sequence in context: A088701 A153698 A168203 * A075066 A061363 A100077
Adjacent sequences: A133594 A133595 A133596 * A133598 A133599 A133600
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KEYWORD
| easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 27 2007
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