cp's OEIS Frontend

A290329 Iterate the map x -> A289667(x) starting at n; sequence gives primes reached, or -1 if no prime is ever reached.

%I A290329 #20 Aug 05 2017 12:38:58
%S A290329 2,3,71,5,71,7,71,11,23,11,5261,13,17,23,703455573449,17,703455573449,
%T A290329 19,5261,71,703455573449,23,727,17,67,
%U A290329 21544131687786037881228990839860266551231,79,29,21544131687786037881228990839860266551231,31,23,239,71,229,227,37,73
%N A290329 Iterate the map x -> A289667(x) starting at n; sequence gives primes reached, or -1 if no prime is ever reached.
%C A290329 Base 3 analog of A195264 and A230627.
%H A290329 Chai Wah Wu, <a href="/A290329/b290329.txt">Table of n, a(n) for n = 2..47</a>
%p A290329 A290329 := proc(n)
%p A290329     local nitr ;
%p A290329     nitr := n ;
%p A290329     while ( not isprime(nitr) and nitr <> 1) do
%p A290329         nitr := A289667(nitr) ;
%p A290329     end do:
%p A290329     return nitr ;
%p A290329 end proc:
%p A290329 seq(A290329(n),n=1..20) ; # _R. J. Mathar_, Aug 05 2017
%t A290329 Table[NestWhile[FromDigits[#, 3] &@ Flatten@ Map[IntegerDigits[#, 3] &, FactorInteger[#] /. {p_, e_} /; p > 0 :> If[e == 1, p, {p, e}]] &, n, ! PrimeQ@ # &], {n, 2, 38}] (* _Michael De Vlieger_, Jul 29 2017 *)
%Y A290329 Cf. A290328, A230627, A289667.
%K A290329 nonn,base
%O A290329 2,1
%A A290329 _Chai Wah Wu_, Jul 27 2017