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A338904
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Irregular triangle read by rows where row n lists all semiprimes whose prime indices sum to n.
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27
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4, 6, 9, 10, 14, 15, 21, 22, 25, 26, 33, 35, 34, 39, 49, 55, 38, 51, 65, 77, 46, 57, 85, 91, 121, 58, 69, 95, 119, 143, 62, 87, 115, 133, 169, 187, 74, 93, 145, 161, 209, 221, 82, 111, 155, 203, 247, 253, 289, 86, 123, 185, 217, 299, 319, 323, 94, 129, 205
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OFFSET
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2,1
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COMMENTS
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A semiprime is a product of any two prime numbers. A prime index of n is a number m such that the m-th prime number divides n. The multiset of prime indices of n is row n of A112798.
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LINKS
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EXAMPLE
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Triangle begins:
4
6
9 10
14 15
21 22 25
26 33 35
34 39 49 55
38 51 65 77
46 57 85 91 121
58 69 95 119 143
62 87 115 133 169 187
74 93 145 161 209 221
82 111 155 203 247 253 289
86 123 185 217 299 319 323
94 129 205 259 341 361 377 391
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MATHEMATICA
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Table[Sort[Table[Prime[k]*Prime[n-k], {k, n/2}]], {n, 2, 10}]
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CROSSREFS
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A087112 is a different triangle of semiprimes.
A098350 has antidiagonals with the same distinct terms as these rows.
A014342 is the self-convolution of primes.
A037143 lists primes and semiprimes.
A056239 gives sum of prime indices (Heinz weight).
A062198 gives partial sums of semiprimes.
A332765 gives the greatest squarefree semiprime of weight n.
Cf. A000040, A001221, A001222, A005117, A112798, A320732, A332877, A338908, A338910, A338911, A339116.
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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