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A140173 Numbers k such that sigma(k) = phi(k)*(sum of the digits of k). 2
1, 6, 3720, 25080, 237000, 353430, 1201560, 1402440, 2104440, 2147040, 4140360, 22007160, 60035220, 104370420, 110095020, 136222020, 402500280, 2203551000, 2223003120, 8720021310, 35590401000, 110232105060, 116046010080, 212062116000, 440401221000, 2181301242120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence is a subsequence of A020492. There is no further term up to 33*10^6. Is it true that 10 divides all multi-digit terms of the sequence?

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..36 (calculated using data from Jud McCranie)

EXAMPLE

sigma(237000) = phi(237000)*(2+3+7+0+0+0).

CROSSREFS

Cf. A020492, A140174.

Sequence in context: A198653 A198660 A048542 * A158663 A110106 A024087

Adjacent sequences:  A140170 A140171 A140172 * A140174 A140175 A140176

KEYWORD

base,nonn

AUTHOR

Farideh Firoozbakht, May 15 2008

EXTENSIONS

7 more terms Sean A. Irvine, Sep 23 2009

a(20)-a(25) from Donovan Johnson, Mar 06 2012

a(26) from Amiram Eldar, Dec 04 2019, using data from Jud McCranie

STATUS

approved

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Last modified October 17 17:21 EDT 2021. Contains 348065 sequences. (Running on oeis4.)