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A339116
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Triangle of all squarefree semiprimes grouped by greater prime factor, read by rows.
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17
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6, 10, 15, 14, 21, 35, 22, 33, 55, 77, 26, 39, 65, 91, 143, 34, 51, 85, 119, 187, 221, 38, 57, 95, 133, 209, 247, 323, 46, 69, 115, 161, 253, 299, 391, 437, 58, 87, 145, 203, 319, 377, 493, 551, 667, 62, 93, 155, 217, 341, 403, 527, 589, 713, 899
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OFFSET
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2,1
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COMMENTS
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A squarefree semiprime is a product of any two distinct prime numbers.
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LINKS
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FORMULA
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T(n,k) = prime(n) * prime(k) for k < n.
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EXAMPLE
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Triangle begins:
6
10 15
14 21 35
22 33 55 77
26 39 65 91 143
34 51 85 119 187 221
38 57 95 133 209 247 323
46 69 115 161 253 299 391 437
58 87 145 203 319 377 493 551 667
62 93 155 217 341 403 527 589 713 899
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MATHEMATICA
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Table[Prime[i]*Prime[j], {i, 2, 10}, {j, i-1}]
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PROG
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(PARI) row(n) = {prime(n)*primes(n-1)}
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CROSSREFS
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A319613 is the central column k = 2*n.
A087112 is the not necessarily squarefree version.
A338905 is a different triangle of squarefree semiprimes.
A339195 is the generalization to all squarefree numbers, row sums A339360.
A024697 is the sum of semiprimes of weight n.
A025129 is the sum of squarefree semiprimes of weight n.
A332765 gives the greatest squarefree semiprime of weight n.
A338904 groups semiprimes by weight.
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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