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Search: id:A123048
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| A123048 |
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Semiprimes that are the sum of a positive square and a positive cube. |
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+0
2
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| 9, 10, 26, 33, 57, 65, 82, 91, 122, 129, 134, 141, 145, 161, 177, 185, 206, 217, 226, 265, 289, 321, 362, 381, 407, 427, 485, 505, 511, 537, 566, 626, 633, 667, 681, 689, 703, 737, 745, 778, 785, 793, 841, 842, 849, 898, 901, 905, 985, 1018, 1041, 1057, 1081
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Semiprime analogue of A066649 Primes of the form a^2 + b^3 with a, b > 0.
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FORMULA
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A001358 INTERSECTION A055394.
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EXAMPLE
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a(1) = 9 = 2^3 + 1^2 = 3*3.
a(2) = 10 = 3^2 + 1^3 = 2*5.
a(3) = 26 = 5^2 + 1^3 = 2*13.
a(4) = 33 = 5^2 + 2^3 = 3*11.
a(5) = 57 = 7^2 + 2^3 = 3*19.
a(6) = 65 = 1^2 + 4^3 = 8^2 + 1^3 = 5*13.
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MATHEMATICA
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semiPrimeQ[x_] := TrueQ[Plus (AT)(AT) Last /(AT) FactorInteger[ x ] == 2]; Select[ Union(AT) Flatten(AT) Table[s^2 + c^3, {s, 10}, {c, 10}], semiPrimeQ(AT)# &] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A001358, A055394, A066649.
Adjacent sequences: A123045 A123046 A123047 this_sequence A123049 A123050 A123051
Sequence in context: A061410 A025043 A111033 this_sequence A041170 A041168 A042635
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Sep 25 2006
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EXTENSIONS
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More terms from Robert G. Wilson v Sep 29 2006
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