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!)
A155878 a(0)=4; for n > 0, a(n) is the smallest composite number c > a(n-1) such that c + n is also composite. 1
4, 8, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 26, 27, 28, 30, 32, 33, 34, 35, 36, 39, 40, 42, 44, 45, 46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 62, 63, 64, 65, 66, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 86, 87, 88, 90, 91, 93, 94, 95, 96, 98, 99, 102, 104, 105, 106, 108 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..67.

EXAMPLE

a(0)=4. Adding a(0) to n=0 gives 4+0=4, which is a composite number; adding a(1) to n=1 gives 8+1=9 which is composite; adding a(2) to n=2 gives 10+2=12 which is composite; adding a(3) to n=3 gives 12+3=15 which is composite; etc.

MAPLE

isA002808 := proc(n) option remember; RETURN(n>= 4 and not isprime(n)) ; end: A155878:= proc(n) option remember; local a; if n = 0 then 4; else for a from procname(n-1)+1 do if isA002808(a) and isA002808(a+n) then RETURN(a) ; fi; od: fi; end: seq(A155878(n), n=0..100) ; # R. J. Mathar, Jan 31 2009

CROSSREFS

Cf. A155874.

Sequence in context: A310974 A310975 A310976 * A029886 A102218 A257586

Adjacent sequences:  A155875 A155876 A155877 * A155879 A155880 A155881

KEYWORD

base,easy,nonn

AUTHOR

Eric Angelini, Jan 29 2009

EXTENSIONS

Extended by R. J. Mathar, Jan 31 2009

Name edited by Jon E. Schoenfield, Jan 20 2019

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 January 24 19:34 EST 2022. Contains 350565 sequences. (Running on oeis4.)