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A228147 Triangle T(n,k), read by rows: T(n,k) is the denominator of (1+2^(n-k+1))/(1-2^(k+1)).

%I A228147 #11 Jan 12 2025 12:15:56
%S A228147 1,1,1,1,3,7,1,1,7,5,1,3,7,3,31,1,1,7,5,31,21,1,3,7,15,31,63,127,1,1,
%T A228147 7,5,31,7,127,85,1,3,7,3,31,63,127,51,511,1,1,7,5,31,21,127,85,511,
%U A228147 341,1,3,7,15,31,63,127,15,511,1023,2047,1,1,7,5,31
%N A228147 Triangle T(n,k), read by rows: T(n,k) is the denominator of (1+2^(n-k+1))/(1-2^(k+1)).
%C A228147 The numerators are given in A228146.
%C A228147 The first diagonal is A213243, the second diagonal is A213244, the third diagonal is A213246, the fourth diagonal is A213247.
%H A228147 Vincenzo Librandi, <a href="/A228147/b228147.txt">Rows n = 0..100, flattened</a>
%e A228147 Triangle begins:
%e A228147 1;
%e A228147 1,1;
%e A228147 1,3,7;
%e A228147 1,1,7,5;
%e A228147 1,3,7,3,31;
%e A228147 1,1,7,5,31,21;
%e A228147 1,3,7,15,31,63,127;
%e A228147 1,1,7,5,31,7,127,85;
%e A228147 1,3,7,3,31,63,127,51,511;
%e A228147 1,1,7,5,31,21,127,85,511,341;
%e A228147 1,3,7,15,31,63,127,15,511,1023,2047;
%e A228147 1,1,7,5,31,21,127,85,511,341,2047,1365; etc.
%t A228147 a[n_, k_] := Denominator[(1 + 2^(n - k + 1))/(1 - 2^(k + 1))]; Table[a[n, k], {n, 0, 11}, {k, 0, n}] // Flatten
%o A228147 (Magma) [Denominator((1+2^(n-k+1))/(1-2^(k+1))): k in [0..n], n in [0..11]];
%Y A228147 Cf. A213243, A213244, A213245, A213246, A213247, A213248.
%K A228147 nonn,tabl
%O A228147 0,5
%A A228147 _Vincenzo Librandi_, Aug 15 2013