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 A122489 Partial sums of A111939 (= number of primes < semiprime(n)). 1
 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; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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). LINKS MATHEMATICA t=PrimePi@Select[Range@218, Plus @@ Last /@ FactorInteger@# == 2 &]; Table[Sum[t[[i]], {i, n}], {n, Length[t]}] (*Chandler*) CROSSREFS Partial sums of A111939(n). Sequence in context: A267531 A219647 A129726 * A120615 A038707 A290140 Adjacent sequences:  A122486 A122487 A122488 * A122490 A122491 A122492 KEYWORD easy,nonn AUTHOR Giovanni Teofilatto, Sep 16 2006 EXTENSIONS Edited and corrected by Ray Chandler, Sep 20 2006 STATUS approved

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Last modified July 20 22:20 EDT 2019. Contains 325189 sequences. (Running on oeis4.)