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%I #11 Oct 30 2019 16:51:47
%S 1,1,1,1,1,2,1,1,1,1,1,4,1,1,1,1,1,1,1,2,2,2,1,1,2,1,2,1,1,2,4,2,1,1,
%T 1,1,1,1,1,1,1,1,1,4,2,4,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,4,2,2,1,1,2,3,
%U 1,3,2,1,1,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,4,2,4,2,4,1,1,1
%N Irregular array: row n has A000010(n) terms: the sum of the first m terms of row n is the m-th positive integer which is coprime to n.
%C The first term of each row is 1. The sum of the terms of row n is n-1, for n>=2. After the initial 1, the remaining terms of each row are the same forward or backward.
%e The positive integers which are <= 12 and are coprime to 12 are 1,5,7,11. Row 12 of the array is: 1,4,2,4. So we have: 1=1; 1+4=5; 1+4+2=7; 1+4+2+4=11.
%e The first 12 rows of the array:
%e 1;
%e 1;
%e 1,1;
%e 1,2;
%e 1,1,1,1;
%e 1,4;
%e 1,1,1,1,1,1;
%e 1,2,2,2;
%e 1,1,2,1,2,1;
%e 1,2,4,2;
%e 1,1,1,1,1,1,1,1,1,1;
%e 1,4,2,4
%t f[n_] := Block[{g},g = Select[Range[n], GCD[ #, n] == 1 &]; g - Prepend[Most[g], 0]]; Flatten[Array[f, 25]] (* _Ray Chandler_, Nov 01 2007 *)
%Y Cf. A038566, A000010.
%K nonn,tabf
%O 1,6
%A _Leroy Quet_, Oct 30 2007
%E Extended by _Ray Chandler_, Nov 01 2007
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