OFFSET
1,1
COMMENTS
Note that before entering the cycle (41, 131, 37, 11) there are 34 terms of the sequence a(1),a(2),...,a(33)=53 and a(34)=173.
LINKS
Carlos Rivera, Puzzle 354.
FORMULA
If k is a natural number then a(4k+31)=41; a(4k+32)=131; a(4k+33)=37 and a(4k+34)=11.
EXAMPLE
a(1)=433640083 so b(1)=nextprime(433640083)=433640093 and c(1)=nextprime(433640093)=433640101 hence a(2) equals largest prime factor of 433640083+433640093+433640101.
But 433640083+433640093+433640101=1300920277 is prime so a(2)= 1300920277.
MATHEMATICA
np[n_]:=Module[{np1=NextPrime[n], np2}, np2=NextPrime[np1]; Max[Transpose[ FactorInteger[n+np1+np2]]]]; NestList[np, 433640083, 50] (* Harvey P. Dale, Sep 22 2011 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Enoch Haga and Farideh Firoozbakht, Apr 08 2006
STATUS
approved