A153427 Numbers n such that phi(n)=p^2, where p is product of digits of n.
1, 12, 125, 451, 4612, 5412, 8313, 22165, 31815, 34125, 43216, 62232, 111398, 115264, 115625, 126225, 142352, 191425, 194313, 235431, 243135, 261532, 265421, 632613, 726313, 852125, 962312, 1142536, 1148316, 1156324, 1162825, 1183491, 1671183, 1672125, 1815912, 1831525, 1914157, 2124535, 2228224, 2321375, 2364132, 2463312, 3356122, 3416541, 3541252, 3716118, 3741812, 4128831, 4218912, 4331236, 4522136, 5148512, 5181293, 5183219, 5463161, 6219612, 6288113, 6411925, 6811922, 7452313, 7518119, 8741341, 9115625, 9324222
Offset: 1
Examples
phi(2228224)=(2*2*2*8*2*2*4)^2, so 2228224 is in the sequence.
Links
- Max Alekseyev, Table of n, a(n) for n = 1..649
Programs
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Mathematica
Do[If[Apply[Times,IntegerDigits[n]]^2==EulerPhi[n],Print[n]],{n,1200000}] Select[Range[94*10^5],EulerPhi[#]==(Times@@IntegerDigits[#])^2&] (* Harvey P. Dale, May 03 2020 *)
Extensions
a(33)-a(649) from Max Alekseyev, Aug 18 2013, May 31 2018