The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A195086 Numbers k such that (number of prime factors of k counted with multiplicity) less (number of distinct prime factors of k) = 2. 14
 8, 24, 27, 36, 40, 54, 56, 88, 100, 104, 120, 125, 135, 136, 152, 168, 180, 184, 189, 196, 225, 232, 248, 250, 252, 264, 270, 280, 296, 297, 300, 312, 328, 343, 344, 351, 375, 376, 378, 396, 408, 424, 440, 441, 450, 456, 459, 468, 472, 484, 488 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS From Amiram Eldar, Nov 07 2020: (Start) Numbers whose powerful part (A057521) is either a cube of a prime (A030078) or a square of a squarefree semiprime (A085986). The asymptotic density of this sequence is (6/Pi^2) * (Sum_{p prime} 1/(p^2*(p+1)) + Sum_{p=4} (-1)^(k+1)*(k-1)*P(k) + (Sum_{k>=2} (-1)^k*P(k))^2))/2 = 0.0963023158..., where P is the prime zeta function. (End) LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Index entries for sequences computed from exponents in factorization of n FORMULA A001222(a(n)) - A001221(a(n)) = 2. A046660(a(n)) = 2. - Reinhard Zumkeller, Nov 29 2015 MATHEMATICA Select[Range[500], PrimeOmega[#]-PrimeNu[#]==2&] PROG (PARI) is(n)=bigomega(n)-omega(n)==2 \\ Charles R Greathouse IV, Sep 14 2015 (PARI) is(n)=my(f=factor(n)[, 2]); vecsum(f)==#f+2 \\ Charles R Greathouse IV, Aug 01 2016 (Haskell) a195086 n = a195086_list !! (n-1) a195086_list = filter ((== 2) . a046660) [1..] -- Reinhard Zumkeller, Nov 29 2015 CROSSREFS Subsequence of A048108. Subsequences: A030078 and A085986. Cf. A001221, A001222, A025487, A057521, A060687, A195069, A195087, A195088, A195089, A195090, A195091, A195092, A195093, A046660, A257851, A261256, A264959. Sequence in context: A295661 A240111 A301517 * A366761 A336593 A176297 Adjacent sequences: A195083 A195084 A195085 * A195087 A195088 A195089 KEYWORD nonn,changed AUTHOR Harvey P. Dale, Sep 08 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 26 13:34 EST 2024. Contains 370352 sequences. (Running on oeis4.)