The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A240975 The number of distinct prime factors of n^3-1. 1
 0, 1, 2, 2, 2, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 4, 2, 2, 3, 2, 3, 3, 4, 2, 4, 3, 3, 2, 4, 3, 4, 3, 2, 3, 4, 4, 4, 2, 4, 3, 3, 3, 4, 3, 4, 4, 4, 3, 4, 2, 4, 3, 4, 2, 4, 4, 3, 4, 3, 3, 5, 2, 4, 4, 3, 3, 5, 3, 3, 3, 4, 3, 3, 4, 3, 3, 3, 3, 5, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Jens Kruse Andersen, Table of n, a(n) for n = 1..10000 FORMULA a(prime(n)) =  A245909(n). a(n) = A001221(A068601(n)). - Michel Marcus, Aug 06 2014 EXAMPLE 3^3-1 = 26 = 2*13, so a(3)=2. 0 has no prime factors, so a(1)=0. MAPLE A240975 := proc(n)     A001221(n^3-1) ; end proc: PROG (Python) from sympy import primefactors def A240975(n): ....return len(primefactors(n**3-1)) # Chai Wah Wu, Aug 06 2014 (PARI) a(n) = if(n<=1, 0, omega(n^3-1)); \\ Joerg Arndt, Aug 06 2014 CROSSREFS Cf. A082863, A245909, A001221. Sequence in context: A139325 A216325 A322868 * A242166 A068211 A236832 Adjacent sequences:  A240972 A240973 A240974 * A240976 A240977 A240978 KEYWORD nonn,easy AUTHOR R. J. Mathar, Aug 05 2014 STATUS approved

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

Last modified September 21 19:57 EDT 2020. Contains 337273 sequences. (Running on oeis4.)