OFFSET
1,4
LINKS
MATHEMATICA
A122111[n_] := Product[Prime[Sum[If[j<i, 0, 1], {j, #}]], {i, Max[#]}]&[ Flatten[Table[Table[PrimePi[f[[1]]], {f[[2]]}], {f, FactorInteger[n]}]]];
a[n_] := With[{k = A122111[n]}, 2k - DivisorSigma[1, k]];
Array[a, 80] (* Jean-François Alcover, Sep 23 2020 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Jan 10 2019
STATUS
approved