The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A365795 Numbers k such that omega(k) = 3 and its prime factors satisfy the equation p_1 + p_2 = p_3. 1
30, 60, 70, 90, 120, 140, 150, 180, 240, 270, 280, 286, 300, 350, 360, 450, 480, 490, 540, 560, 572, 600, 646, 700, 720, 750, 810, 900, 960, 980, 1080, 1120, 1144, 1200, 1292, 1350, 1400, 1440, 1500, 1620, 1750, 1798, 1800, 1920, 1960, 2160, 2240, 2250, 2288, 2400, 2430, 2450 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The lower prime factor p_1 is equal to 2 and the other two are twin primes: p_3 - p_2 = 2.
LINKS
EXAMPLE
60 is a term since 60 = 2^2*3*5 and 2 + 3 = 5.
286 is a term since 286 = 2*11*13 and 2 + 11 = 13.
MATHEMATICA
Select[Range[2500], PrimeNu[#]==3&&Part[First/@FactorInteger[#], 1]+Part[First/@FactorInteger[#], 2]==Part[First/@FactorInteger[#], 3]&]
PROG
(PARI) isok(k) = if (omega(k)==3, my(f=factor(k)[, 1]); f[1] + f[2] == f[3]); \\ Michel Marcus, Sep 19 2023
CROSSREFS
Subsequence of A033992 and of A071140.
Sequence in context: A291046 A071140 A221054 * A074915 A073461 A222618
KEYWORD
nonn
AUTHOR
Stefano Spezia, Sep 19 2023
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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 27 12:27 EDT 2024. Contains 372858 sequences. (Running on oeis4.)