A064125 Numbers k such that k and k+1 have the same sum of unitary divisors (A034448).

14, 44, 55, 152, 957, 1334, 1400, 1634, 1652, 2204, 2232, 2295, 2685, 3195, 3451, 3956, 4256, 5547, 7191, 8216, 8495, 8636, 8907, 9144, 9503, 9844, 10152, 11515, 17255, 18423, 19491, 20145, 20155, 27404, 27643, 30247, 33998, 38180, 41265

Offset: 1

Author

Jason Earls, Sep 10 2001

Keywords

• easy
• nonn

Links

• Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 800 terms from Harry J. Smith)

Programs

PARI

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

PARI

usigma(n)= { local(f,s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) }
{ n=0; s=0; for (m=1, 10^9, us=usigma(m+1); if(s==us, write("b064125.txt", n++, " ", m); if (n==800, break)); s=us ) } \\ Harry J. Smith, Sep 08 2009