A140173 Numbers k such that sigma(k) = phi(k)*(sum of the digits of k).

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

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