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A362213 Irregular table read by rows in which the n-th row consists of all the numbers m such that cototient(m) = n, where cototient is A051953.

%I A362213 #11 Apr 12 2023 08:05:50
%S A362213 4,9,6,8,25,10,15,49,12,14,16,21,27,35,121,18,20,22,33,169,26,39,55,
%T A362213 24,28,32,65,77,289,34,51,91,361,38,45,57,85,30,95,119,143,529,36,40,
%U A362213 44,46,69,125,133,63,81,115,187,52,161,209,221,841,42,50,58,87,247,961
%N A362213 Irregular table read by rows in which the n-th row consists of all the numbers m such that cototient(m) = n, where cototient is A051953.
%C A362213 The offset is 2 since cototient(p) = 1 for all primes p.
%C A362213 The 0th row consists of one term, 1, since 1 is the only solution to cototient(x) = 0.
%H A362213 Amiram Eldar, <a href="/A362213/b362213.txt">Table of n, a(n) for n = 2..9674</a> (rows 2..1000)
%e A362213 The table begins:
%e A362213   n   n-th row
%e A362213   --  -----------
%e A362213    2  4;
%e A362213    3  9;
%e A362213    4  6, 8;
%e A362213    5  25;
%e A362213    6  10;
%e A362213    7  15, 49;
%e A362213    8  12, 14, 16;
%e A362213    9  21, 27;
%e A362213   10
%e A362213   11  35, 121;
%e A362213   12  18, 20, 22;
%t A362213 With[{max = 50}, cot = Table[n - EulerPhi[n], {n, 1, max^2}]; row[n_] := Position[cot, n] // Flatten; Table[row[n], {n, 2, max}] // Flatten]
%Y A362213 Cf. A005278, A051953, A063507, A063740 (row lengths), A063741, A063742, A063748, A100827, A101373, A131825, A131826.
%Y A362213 Similar sequences: A032447, A361966, A362180.
%K A362213 nonn,tabf
%O A362213 2,1
%A A362213 _Amiram Eldar_, Apr 11 2023