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A348265
a(n) is the least number k such that A348264(k) = n, or -1 if no such number exists.
0
1, 2, 84, 1596, 410652, 9114300, 10628100, 3012406320
OFFSET
0,2
EXAMPLE
n The n iterations of a(n) under the map x -> A348264(x)
- --------------------------------------------------------------------------------
0 1
1 2 -> 1
2 84 -> 78 -> 39
3 1596 -> 1428 -> 1326 -> 663
4 410652 -> 410172 -> 366996 -> 340782 -> 170391
5 9114300 -> 8871252 -> 8680848 -> 8661648 -> 8487018 -> 4243509
6 10628100 -> 10344684 -> 10309980 -> 10287900 -> 10013556 -> 9298302 -> 4649151
7 3012406320 -> 2999958360 -> 2927545572 -> 2917724340 -> 2911475700 -> 2833836348 -> 2631419466 -> 1315709733
MATHEMATICA
f[p_, e_] := p^e - 1; uphi[1] = 1; uphi[n_] := Times @@ f @@@ FactorInteger[n]; sum[n_] := Plus @@ DeleteDuplicates[uphi /@ Select[Divisors[n], CoprimeQ[#, n/#] &]]; s[n_] := -2 + Length@FixedPointList[sum, n]; seq[m_, lim_] := Module[{t = Table[0, {m}], c = 0, n = 1}, While[c < m && n < lim, i = s[n] + 1; If[i <= m && t[[i]] == 0, c++; t[[i]] = n]; n++]; TakeWhile[t, # > 0 &]]; seq[5, 10^6]
CROSSREFS
The unitary version of A348214.
Sequence in context: A205643 A215263 A265591 * A157063 A372716 A288312
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Oct 09 2021
STATUS
approved