OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
MATHEMATICA
Module[{nn=700, s, p}, s=Accumulate[DivisorSigma[1, Range[nn]]]; p=FoldList[ Times, EulerPhi[ Range[nn]]]; Position[ Thread[{s, p}], _?(Mod[#[[2]], #[[1]]]==0&), 1, Heads->False]]//Flatten (* Harvey P. Dale, Feb 28 2024 *)
PROG
(PARI) j=[]; for(n=1, 1300, a=sum(k=1, n, sigma(k)); b=prod(k=1, n, eulerphi(k)); if(Mod(b, a)==0, j=concat(j, n))); j
(PARI) { n=0; s=0; p=1; for (m=1, 10^9, s+=sigma(m); p*=eulerphi(m); if(p%s == 0, write("b063770.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 30 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Aug 15 2001
STATUS
approved