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A064125
Numbers k such that k and k+1 have the same sum of unitary divisors (A034448).
32
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
1,1
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 800 terms from Harry J. Smith)
PROG
(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
CROSSREFS
Sequence in context: A041380 A151990 A156166 * A089031 A265152 A033587
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Sep 10 2001
STATUS
approved