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

1,2

Links

Max Alekseyev, Table of n, a(n) for n = 1..649

Example

phi(2228224)=(2*2*2*8*2*2*4)^2, so 2228224 is in the sequence.

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 *)

Crossrefs

Cf. A068572, A153428.

Sequence in context: A209041 A155595 A070312 * A356822 A178626 A223322

Adjacent sequences: A153424 A153425 A153426 * A153428 A153429 A153430

Keyword

base,nonn

Author

Farideh Firoozbakht, Jan 02 2009

Extensions

a(33)-a(649) from Max Alekseyev, Aug 18 2013, May 31 2018

Status

approved