OFFSET
1,2
MATHEMATICA
A018804[n_]:=Apply[Times, Apply[((#1-1)#2/#1+1)#1^#2&, FactorInteger[n], {1}]]; (* After Amiram Eldar in A018804 *)
upto=10^5; Reap[Do[If[IntegerQ[A018804[k]/DivisorSigma[1, k]], Sow[k]], {k, upto}]][[-1, -1]] (* Paolo Xausa, Aug 18 2022 *)
PROG
(PARI) isok(k) = (sumdiv(k, d, k*eulerphi(d)/d) % sigma(k)) == 0; \\ Michel Marcus, Nov 27 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Nov 27 2021
EXTENSIONS
a(12)-a(36) from Paolo Xausa, Nov 27 2021
More terms from Amiram Eldar, Nov 27 2021
STATUS
approved