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A072604 Last digit of n, phi(n) and sigma(n) is 0 in base 10. 1
440, 600, 950, 1000, 1240, 1320, 1350, 1400, 1450, 1640, 1900, 2090, 2200, 2440, 2600, 2700, 2840, 2850, 2900, 2950, 2970, 3000, 3080, 3190, 3400, 3720, 3800, 3950, 3960, 4040, 4180, 4200, 4350, 4450, 4600, 4750, 4840, 4920, 5240, 5400, 5450, 5700 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is infinite. 440 * k is in the sequence for odd k > 0 and k, 440 are coprime. - David A. Corneth, Apr 01 2018

LINKS

David A. Corneth, Table of n, a(n) for n = 1..16811 (all terms up to 10^6)

FORMULA

Does lim n -> infinity a(n)/n exist?

EXAMPLE

phi(1240)=480, sigma(1240)=2880, hence 1240 is in the sequence.

MATHEMATICA

Select[Range[6000], Mod[{#, EulerPhi[#], DivisorSigma[1, #]}, 10]=={0, 0, 0}&] (* Harvey P. Dale, Apr 01 2018 *)

PROG

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

CROSSREFS

Cf. A000010, A000203.

Subsequence of A072589.

Sequence in context: A296905 A279812 A279950 * A158319 A250879 A247722

Adjacent sequences:  A072601 A072602 A072603 * A072605 A072606 A072607

KEYWORD

base,nonn

AUTHOR

Benoit Cloitre, Aug 06 2002

STATUS

approved

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Last modified October 25 19:28 EDT 2020. Contains 338012 sequences. (Running on oeis4.)