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A339194
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Sum of all squarefree semiprimes with greater prime factor prime(n).
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7
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0, 6, 25, 70, 187, 364, 697, 1102, 1771, 2900, 3999, 5920, 8077, 10234, 13207, 17384, 22479, 26840, 33567, 40328, 46647, 56248, 65653, 77786, 93411, 107060, 119583, 135248, 149439, 167240, 202311, 225320, 253587, 276332, 316923, 343676, 381039, 421192, 458749
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = prime(n) * Sum_{k=1..n-1} prime(k) = prime(n) * A007504(n-1).
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EXAMPLE
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The triangle A339116 with row sums equal to this sequence begins (n > 1):
6 = 6
25 = 10 + 15
70 = 14 + 21 + 35
187 = 22 + 33 + 55 + 77
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MATHEMATICA
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Table[Sum[Prime[i]*Prime[j], {j, i-1}], {i, 10}]
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PROG
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(PARI) a(n) = prime(n)*vecsum(primes(n-1)); \\ Michel Marcus, Jun 15 2024
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CROSSREFS
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A025129 gives sums of squarefree semiprimes by weight, row sums of A338905.
A143215 is the not necessarily squarefree version, row sums of A087112.
A339116 is a triangle of squarefree semiprimes with these row sums.
A024697 is the sum of semiprimes of weight n.
A168472 gives partial sums of squarefree semiprimes.
A332765 gives the greatest squarefree semiprime of weight n.
A338904 groups semiprimes by weight.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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