OFFSET
1,2
EXAMPLE
If n=12, then 12/4*(c(12)-r(12))=3/(21-18)=1=a(1).
If n=48, then 48/4*(c(48)-r(48))=12/(68-65)=4=a(2).
If n=64, then 64/4*(c(64)-r(64))=16/(76-74)=8=a(3).
If n=72, then 72/4*(c(72)-r(72))=18/(98-95)=6=a(4).
If n=96, then 96/4*(c(96)-r(96))=24/(117-115)=12=a(5), etc.
MAPLE
A141468 := proc(n) option remember ; if n = 1 then 0; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od: fi; end: A002808 := proc(n) option remember ; A141468(n+2) ; end: for n from 1 to 3000 do p := n/(A002808(n)-A141468(n))/4 ; if type(p, 'integer') then if not isprime(p) then printf("%d, ", p) ; fi; fi; od: # R. J. Mathar, Jan 23 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Sep 21 2008
EXTENSIONS
Corrected and extended by R. J. Mathar, Jan 23 2009
STATUS
approved