A072589 n, phi(n) and sigma(n) end with the same digit.

1, 84, 204, 294, 364, 440, 444, 564, 600, 644, 804, 884, 950, 1000, 1134, 1164, 1204, 1240, 1274, 1284, 1320, 1344, 1350, 1400, 1450, 1484, 1524, 1564, 1640, 1644, 1734, 1884, 1900, 1924, 2004, 2044, 2090, 2200, 2254, 2324, 2364, 2440, 2444, 2600, 2700, 2724

Offset

1,2

Links

Table of n, a(n) for n=1..46.

Formula

It seems that lim n -> infinity a(n)/n exists around 40.

Mathematica

Select[Range[3000], Last[IntegerDigits[#]]==Last[ IntegerDigits[ EulerPhi[ #]]] == Last[ IntegerDigits[ DivisorSigma[1, #]]]&] (* Harvey P. Dale, Aug 03 2014 *)

Prog

(PARI) isok(n) = ((n % 10) == (eulerphi(n) % 10)) && ((n % 10) == (sigma(n) % 10)); \\ Michel Marcus, Nov 26 2013

Crossrefs

Intersection of A072566 and A072585.

Cf. A000010, A000203.

Sequence in context: A306514 A044416 A044797 * A181113 A254464 A135804

Adjacent sequences: A072586 A072587 A072588 * A072590 A072591 A072592

Keyword

base,nonn

Author

Benoit Cloitre, Aug 06 2002

Status

approved