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Search: id:A076290
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| A076290 |
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Sum of the semiprime divisors of n. |
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+0
1
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| 0, 0, 0, 4, 0, 6, 0, 4, 9, 10, 0, 10, 0, 14, 15, 4, 0, 15, 0, 14, 21, 22, 0, 10, 25, 26, 9, 18, 0, 31, 0, 4, 33, 34, 35, 19, 0, 38, 39, 14, 0, 41, 0, 26, 24, 46, 0, 10, 49, 35, 51, 30, 0, 15, 55, 18, 57, 58, 0, 35, 0, 62, 30, 4, 65, 61, 0, 38, 69, 59, 0, 19, 0, 74, 40, 42, 77, 71, 0
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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A semiprime is a product of two primes.
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EXAMPLE
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The divisors of 12 are 1, 2, 3, 4, 6, 12, of which 4 and 6 are semiprime. Hence a(12) = 4 + 6 = 10.
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MATHEMATICA
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isSP[n_] := Module[{f, l}, f = FactorInteger[n]; l = Length[f]; (l == 2 && f[[1]][[2]] == 1 && f[[2]][[2]] == 1) || (l == 1 && f[[1]][[2]] == 2)]; f[n_] := Module[{a, d, l}, a = {}; d = Divisors[n]; l = Length[d]; For[i = 1, i <= l, i++, If[isSP[d[[i]]], a = Append[a, d[[i]]]]]; a]; Table[Apply[Plus, f[i]], {i, 1, 100}]
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CROSSREFS
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Cf. A001358.
Sequence in context: A056141 A125961 A016681 this_sequence A055672 A085562 A037282
Adjacent sequences: A076287 A076288 A076289 this_sequence A076291 A076292 A076293
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KEYWORD
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easy,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Nov 24 2002
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