OFFSET
1,8
LINKS
FORMULA
a(A331285(n)) = n for all n.
MATHEMATICA
c[n_] := c[n] = If[n == 1, 1, Module[{f = FactorInteger[n], p, e}, If[Length[f] > 1, Times @@ c /@ Power @@@ f, {{p, e}} = f; Times @@ (Prime[Range[PrimePi[p]]]^e)]]];
A329605[n_] := DivisorSigma[0, c[n]];
Module[{b}, b[_] = 0;
a[n_] := With[{t = A329605[n]}, b[t] = b[t] + 1]];
Array[a, 105] (* Jean-François Alcover, Jan 12 2022 *)
PROG
(PARI)
up_to = 65537;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om, invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om, invec[i], (1+pt))); outvec; };
A329605(n) = if(1==n, 1, my(f=factor(n), e=1, m=1); forstep(i=#f~, 1, -1, e += f[i, 2]; m *= e^(primepi(f[i, 1])-if(1==i, 0, primepi(f[i-1, 1])))); (m));
v331284 = ordinal_transform(vector(up_to, n, A329605(n)));
A331284(n) = v331284[n];
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 14 2020
STATUS
approved