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A251362
Numbers n such that n is the concatenation of distinct prime factors of phi(n), in increasing order.
3
25, 235741, 23517131
OFFSET
1,1
COMMENTS
Next term must be greater than 10^8.
Numbers n such that n = A084317(A000010(n)). - Michel Marcus, Dec 06 2014
EXAMPLE
25 is in the sequence since phi(25)=2^2*5, 235741 is in the sequence since phi(235741)=2^4*3^2*5*7*41, and 23517131 is in the sequence since phi(23517131)=2^7*3*5^2*17*131.
MATHEMATICA
a251362[n_Integer] := Rest@ Select[Range[n], # ==
FromDigits[Flatten@IntegerDigits[First@Transpose@FactorInteger[EulerPhi[#]]]] &]; a251362[10^6] (* Michael De Vlieger, Dec 03 2014 *)
CROSSREFS
KEYWORD
nonn,base,more,bref
AUTHOR
Jahangeer Kholdi, Dec 03 2014
STATUS
approved