OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n=1..1000
FORMULA
MATHEMATICA
usigma[n_] := DivisorSum[n, Boole[CoprimeQ[#, n/#]]*#& ]; a[n_] := DivisorSigma[1, usigma[n]]; Array[a, 60] (* Jean-François Alcover, Dec 02 2015 *)
PROG
(PARI) usigma(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) { for (n=1, 1000, write("b063845.txt", n, " ", sigma(usigma(n))) ) } \\ Harry J. Smith, Sep 01 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Oct 30 2001
STATUS
approved