A063968 Numbers k such that sopf(k) = sopf(k+2), where sopf(k) = A008472(k).

2, 340, 845, 950, 1340, 3724, 5694, 6102, 7657, 8991, 9331, 9709, 10323, 11388, 11390, 12460, 15870, 18912, 19778, 20882, 21715, 24732, 26978, 29052, 29632, 32428, 33596, 35028, 38178, 42718, 43068, 45750, 46102, 50396, 53251, 61408

Offset: 1

Author

Jason Earls, Sep 05 2001

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Crossrefs

Cf. A008472, A006145.

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=1,100000, if(sopf(n)==sopf(n+2),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; r=sopf(1); s=sopf(2); for (m=1, 10^9, t=sopf(m + 2); if(r==t, write("b063968.txt", n++, " ", m); if (n==1000, break)); r=s; s=t ) } \\ Harry J. Smith, Sep 04 2009