cp's OEIS Frontend

A355606 The indices where A354606(n) = 1.

%I A355606 #12 Dec 12 2024 11:02:06
%S A355606 1,2,4,9,14,25,37,57,99,133,182,191,404,469,595,640,780,1195,1884,
%T A355606 2407,2808,3010,3217,3444,4245,4383,5773,8703,10069,10731,12640,14470,
%U A355606 17998,18535,22648,23341,24286,27431,33702,37019,45593,53759,56598,57578,76640,96729,99557,106881,125900,144162
%N A355606 The indices where A354606(n) = 1.
%C A355606 See A354606 for further details.
%t A355606 c[_] := 0; j = 1; nn = 2^20; {1}~Join~Reap[Monitor[Do[k = ++c[DivisorSigma[0, j]]; If[k == 1, Sow[n]]; j = k, {n, 2, nn}], n] ][[-1, 1]] (* _Michael De Vlieger_, Dec 12 2024 *)
%o A355606 (Python)
%o A355606 from sympy import divisor_count
%o A355606 from collections import Counter
%o A355606 from itertools import count, islice
%o A355606 def f(n): return divisor_count(n)
%o A355606 def agen():
%o A355606     n, an, fan, inventory = 1, 1, 1, Counter([1])
%o A355606     yield n
%o A355606     for n in count(2):
%o A355606         an = inventory[fan]
%o A355606         fan = f(an)
%o A355606         inventory.update([fan])
%o A355606         if an == 1: yield n
%o A355606 print(list(islice(agen(), 50))) # _Michael S. Branicky_, Jul 09 2022
%Y A355606 Cf. A354606, A000005.
%K A355606 nonn
%O A355606 1,2
%A A355606 _Scott R. Shannon_, Jul 09 2022