A063969 - OEIS

%I #19 Jun 25 2018 03:43:20

%S 7,60,147,407,470,1053,1175,3431,3822,5126,5960,6280,6321,6897,7200,

%T 8687,9243,10760,12614,15093,16153,18080,18818,19668,20433,20976,

%U 24648,26826,30804,44016,45878,46221,47423,55965,58506,58682,59645,63897

%N Numbers k such that sopf(k) = sopf(k+3), where sopf(k) = A008472(k).

%H Giovanni Resta, <a href="/A063969/b063969.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Harry J. Smith)

%t Select[Range[65000],Total[Transpose[FactorInteger[#]][[1]]] == Total[ Transpose[FactorInteger[#+3]][[1]]]&] (* _Harvey P. Dale_, Jan 19 2013 *)

%o (PARI) sopf(n,s,fac,i)=fac=factor(n); for(i=1,matsize(fac)[1],s=s+fac[i,1]); return(s);

%o j=[]; for(n=1,100000, if(sopf(n)==sopf(n+3),j=concat(j,n))); j

%o (PARI) sopf(n)= { local(f,s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]); return(s) }

%o { n=0; for (m=1, 10^9, if(sopf(m)==sopf(m + 3), write("b063969.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Sep 04 2009

%Y Cf. A008472, A006145.

%K nonn

%O 1,1

%A _Jason Earls_, Sep 05 2001