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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A141219 Write the n-th nonprime (A018252(n)) as a product of primes; increase one copy of the largest prime by 1 and decrease one copy of the smallest prime by 1, multiply the resulting numbers. 3

%I

%S 1,3,4,6,8,6,8,8,12,12,12,12,16,12,16,24,14,24,16,18,24,24,18,32,24,

%T 20,28,24,24,24,36,24,32,48,30,36,28,36,48,32,40,30,36,32,48,48,56,36,

%U 36,48,40,48,38,60,40,72,42,48,72,42,48,72,44,60,48,54,84

%N Write the n-th nonprime (A018252(n)) as a product of primes; increase one copy of the largest prime by 1 and decrease one copy of the smallest prime by 1, multiply the resulting numbers.

%e 1st nonprime = 1 (has no prime factors); a(1) = empty product = 1.

%e 2nd nonprime = 4 = (p(max)=2)*(p(min)=2); a(2) = (2+1)*(2-1) = 3*1 = 3.

%e 3rd nonprime = 6 = (p(max)=3)*(p(min)=2); a(3) = (3+1)*(2-1) = 4*1 = 4.

%e 4th nonprime = 8 = (p(max)=2)*(p=2)*(p(min)=2); a(4) = (2+1)*2*(2-1) = 3*2*1 = 6.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Aug 07 2008

%E Three terms corrected by _R. J. Mathar_, Aug 18 2008

%E Entry revised by _Jon E. Schoenfield_, Mar 09 2014, following revision of A141218 by _N. J. A. Sloane_

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 28 12:34 EDT 2020. Contains 337393 sequences. (Running on oeis4.)