OFFSET
1,1
EXAMPLE
If n=24, then 24/4*(c(24)-r(24))=6/(36-34)=2=a(1).
If n=40, then 40/4*(c(40)-r(40))=10/(48-44)=5=a(2).
If n=42, then 42/4*(c(42)-r(42))=42/4*(48-45)=7=a(3).
If n=60, then 60/4*(c(60)-r(60))=15/(84-81)=5=a(4).
If n=80, then 80/4*(c(80)-r(80))=20/(110-106)=5=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 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