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
Examples
sigma(237000) = phi(237000)*(2+3+7+0+0+0).
Links
- Amiram Eldar, Table of n, a(n) for n = 1..36 (calculated using data from _Jud McCranie_)
Programs
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Mathematica
Select[Range[10^6],DivisorSigma[1,#]==EulerPhi[#]*DigitSum[#]&] (* James C. McMahon, Jul 06 2025 *)
Extensions
a(13)-a(19) from 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
Comments