A251363 - OEIS

%I #20 Dec 10 2014 18:02:57

%S 237532,832332,82953292

%N Numbers n such that n is the concatenation of distinct prime factors of phi(n), in decreasing order.

%C Next term is greater than 1.6*10^8.

%C Numbers n such that n = A085307(A000010(n)). - _Michel Marcus_, Dec 06 2014

%e 237532 is in the sequence since phi(237532)=23*7*5*3^2*2^4,

%e 832332 is in the sequence since phi(832332)=83*23*3^2*2^4, and

%e 82953292 is in the sequence since phi(82953292)=829*53*29*2^5.

%t a251363[n_Integer] :=

%t Rest@ Select[Range[n], # == FromDigits[Flatten@ IntegerDigits[

%t Sort[First@ Transpose@ FactorInteger[EulerPhi[#]], Greater]]] &]; a251363[10^6] (* _Michael De Vlieger_, Dec 03 2014 *)

%Y Cf. A000010, A000040, A085307, A251362.

%K nonn,base,more,bref

%O 1,1

%A _Jahangeer Kholdi_, Dec 03 2014