A063846 Numbers k such that sigma(k) - usigma(k) > 2k.

1440, 1800, 2160, 2880, 3024, 3600, 4320, 5040, 5400, 5760, 6048, 6480, 7056, 7200, 7560, 7920, 8064, 8640, 9000, 9072, 9360, 9504, 9720, 10080, 10584, 10800, 11088, 11520, 11880, 12096, 12240, 12600, 12960, 13680, 14040, 14112, 14400, 15120

Offset: 1

Author

Jason Earls, Aug 25 2001

Keywords

• easy
• nonn

Links

• Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 1000 terms from Harry J. Smith)

Crossrefs

Cf. A034448, A048146, A034683, A064597.

Programs

PARI

u(n) = sumdiv(n,d, if(gcd(d,n/d)==1,d));
j=[]; for(n=1,20000, if(sigma(n)-u(n)>2*n,j=concat(j,n))); j

PARI

u(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d))
{ n=0; for (m=1, 10^9, if(sigma(m) - u(m) > 2*m, write("b063846.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Sep 01 2009