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!)
A079772 Let C(n) be the n-th composite number; then a(n) is the smallest number > C(n) and not coprime to C(n). 0
6, 8, 10, 12, 12, 14, 16, 18, 18, 20, 22, 24, 24, 26, 30, 28, 30, 30, 32, 34, 36, 36, 40, 38, 40, 42, 42, 44, 46, 48, 48, 50, 56, 52, 54, 54, 56, 60, 58, 60, 60, 62, 64, 66, 66, 70, 68, 70, 72, 72, 74, 76, 78, 78, 84, 80, 82, 84, 84, 86, 90, 88, 90, 90, 92, 98, 94, 96, 96, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = A002808(n) + A056608(n). - Vladeta Jovovic, Jan 31 2003

LINKS

Table of n, a(n) for n=1..70.

FORMULA

a(n) = C(n) + smallest prime divisor of C(n).

EXAMPLE

C(4) = 9 and C(5) = 10 hence a(4) = a(5) = 12.

For 91=7*13 we have 91+7 = 98; for 92=2*2*23 we have 92-2 = 94

PROG

(PARI) cminusp31(n) = \sum c+min prime div { for(x=2, n, forprime(p=2, floor(sqrt(x)), if(x%p==0 & isprime(x)==0, print1(x+p, ", "); break); ) ) }

CROSSREFS

Sequence in context: A171562 A018221 A071278 * A080731 A080257 A331201

Adjacent sequences:  A079769 A079770 A079771 * A079773 A079774 A079775

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Jan 31 2003

EXTENSIONS

More terms from Cino Hilliard, Aug 12 2003

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 15 13:25 EDT 2021. Contains 345048 sequences. (Running on oeis4.)