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 A101041 Number of numbers not greater than n having no more than two prime factors. 1
 1, 2, 3, 4, 5, 6, 7, 7, 8, 9, 10, 10, 11, 12, 13, 13, 14, 14, 15, 15, 16, 17, 18, 18, 19, 20, 20, 20, 21, 21, 22, 22, 23, 24, 25, 25, 26, 27, 28, 28, 29, 29, 30, 30, 30, 31, 32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 37, 38, 39, 39, 40, 41, 41, 41, 42, 42, 43, 43, 44, 44, 45, 45, 46 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = 1 + Sum_{k=1..n} A101040(k); asymptotically: a(n) ~ n*log(log(n))/log(n). Primes counted with multiplicity. - Harvey P. Dale, Feb 16 2024 LINKS Table of n, a(n) for n=1..73. FORMULA a(n) = A000720(n) + A072000(n) + 1. MATHEMATICA Accumulate[Table[If[PrimeOmega[n]<3, 1, 0], {n, 80}]] (* Harvey P. Dale, Feb 16 2024 *) CROSSREFS Cf. A000720, A072000, A101040. Sequence in context: A271490 A252649 A095703 * A093697 A157466 A194260 Adjacent sequences: A101038 A101039 A101040 * A101042 A101043 A101044 KEYWORD nonn AUTHOR Reinhard Zumkeller, Nov 28 2004 STATUS approved

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Last modified August 13 16:51 EDT 2024. Contains 375144 sequences. (Running on oeis4.)