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Search: id:A122489
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| A122489 |
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Partial sums of A111939 (= number of primes < semiprime(n)). |
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+0
2
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| 2, 5, 9, 13, 19, 25, 33, 41, 50, 59, 70, 81, 92, 104, 116, 130, 145, 160, 176, 192, 208, 226, 244, 263, 284, 305, 327, 350, 373, 396, 420, 444, 468, 492, 519, 548, 578, 608, 638, 668, 698, 728, 759, 791, 823, 857, 891, 925, 959, 993, 1029, 1066, 1103, 1140
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Perfect powers occur at the following terms:
a(3) = 9 = 3^2
a(6) = 25 = 5^2
a(12) = 81 = 3^4
a(74) = 2025 = 45^2
a(2072) = 1062961 = 1031^2
a(43881) = 392713489 = 19817^2
a(134249) = 3497963832 = 1518^3
a(372727) = 25930982961 = 161031^2
a(1196234) = 257007427681 = 506959^2
a(1449506) = 375159925009 = 612503^2
a(5226094) = 4704717169296 = 2169036^2
a(8342271) = 11846166214276 = 3441826^2
a(62507725) = 635490555087844 = 25208938^2
a(91695024) = 1356954402007044 = 36836862^2
No further perfect powers through a(10^8).
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MATHEMATICA
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t=PrimePi@Select[Range@218, Plus @@ Last /@ FactorInteger@# == 2 &]; Table[Sum[t[[i]], {i, n}], {n, Length[t]}] (*Chandler*)
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CROSSREFS
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Partial sums of A111939(n).
Sequence in context: A055025 A130235 A129726 this_sequence A120615 A038707 A071705
Adjacent sequences: A122486 A122487 A122488 this_sequence A122490 A122491 A122492
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Sep 16 2006
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EXTENSIONS
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Edited and corrected by Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 20 2006
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