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A341218 a(n) is the number of numbers k such that A340873(k) = n.

%I A341218 #8 Feb 09 2021 11:01:51
%S A341218 1,1,1,2,3,4,6,8,11,15,21,29,40,54,74,102,139,189,259,355,486,664,908,
%T A341218 1242,1697,2317,3165,4326,5911,8076,11034,15073,20588,28125,38415,
%U A341218 52477,71692,97931,133774,182739,249634,341013,465839,636346,869279,1187486
%N A341218 a(n) is the number of numbers k such that A340873(k) = n.
%H A341218 Rémy Sigrist, <a href="/A341218/a341218.gp.txt">PARI program for A341218</a>
%H A341218 <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>
%F A341218 a(n) <= a(n+1) <= 2*a(n).
%e A341218 The first terms, alongside the correspond k's, are:
%e A341218    n  a(n)  k's
%e A341218    -  ----  ----------------------
%e A341218    0     1              1
%e A341218                         |
%e A341218    1     1              2
%e A341218                         |
%e A341218    2     1              4
%e A341218                        / \
%e A341218    3     2            3   8
%e A341218                      /   / \
%e A341218    4     3          6   7   16
%e A341218                    /   /   /  \
%e A341218    5     4       12  14  15    32
%o A341218 (PARI) See Links section.
%Y A341218 Cf. A005186, A340873.
%K A341218 nonn,base
%O A341218 0,4
%A A341218 _Rémy Sigrist_, Feb 07 2021