A064112 Numbers k such that sopf(k) = 2*sopf(k+1), where sopf(k) = A008472.

99, 155, 689, 1106, 1517, 1524, 3014, 3403, 3479, 5809, 6478, 6723, 8606, 9143, 9454, 9797, 10126, 11771, 12283, 12382, 13112, 13969, 14150, 17422, 19303, 22184, 24856, 27466, 28119, 28529, 35927, 36464, 37512, 41904, 44505, 45016, 45506

Offset: 1

Author

Jason Earls, Sep 08 2001

Keywords

• nonn

Examples

			sopf(689)=66, 2*sopf(690)=66.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..600 from Harry J. Smith)

Crossrefs

Cf. A008472 (sopf).

Programs

PARI

sopf(n, s, fac, i) = fac=factor(n); for(i=1,matsize(fac)[1],s=s+fac[i,1]); return(s);
j=[]; for(n=1,50000, if(sopf(n)==2*sopf(n+1),j=concat(j,n))); j

PARI

sopf(n)= { local(f,s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]); return(s) }
{ n=0; sm=sopf(1); for (m=1, 10^9, sp=sopf(m + 1); if (sm==2*sp, write("b064112.txt", n++, " ", m); if (n==600, break)); sm=sp ) } \\ Harry J. Smith, Sep 07 2009