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A381398 Irregular triangle read by rows, where row n lists the elements of the set of bases and exponents (including exponents = 1) in the prime factorization of n.

%I A381398 #11 Feb 25 2025 11:39:24
%S A381398 1,2,1,3,2,1,5,1,2,3,1,7,2,3,2,3,1,2,5,1,11,1,2,3,1,13,1,2,7,1,3,5,2,
%T A381398 4,1,17,1,2,3,1,19,1,2,5,1,3,7,1,2,11,1,23,1,2,3,2,5,1,2,13,3,1,2,7,1,
%U A381398 29,1,2,3,5,1,31,2,5,1,3,11,1,2,17,1,5,7,2,3
%N A381398 Irregular triangle read by rows, where row n lists the elements of the set of bases and exponents (including exponents = 1) in the prime factorization of n.
%H A381398 Paolo Xausa, <a href="/A381398/b381398.txt">Table of n, a(n) for n = 2..10326</a> (rows 2..3000 of triangle, flattened).
%e A381398 Triangle begins:
%e A381398    [2]  1, 2;
%e A381398    [3]  1, 3;
%e A381398    [4]  2;
%e A381398    [5]  1, 5;
%e A381398    [6]  1, 2, 3;
%e A381398    [7]  1, 7;
%e A381398    [8]  2, 3;
%e A381398    [9]  2, 3;
%e A381398   [10]  1, 2, 5;
%e A381398   ...
%e A381398 The prime factorization of 10 is 2^1*5^1 and the set of these bases and exponents is {1, 2, 5}.
%t A381398 A381398row[n_] := Union[Flatten[FactorInteger[n]]];
%t A381398 Array[A381398row, 50, 2]
%Y A381398 Cf. A381201 (row products), A381202 (row sums), A381205 (row lengths).
%Y A381398 Cf. A381203 (row lcms), A381204 (row gcds).
%Y A381398 Cf. A081812 (row largest elements), A381212 (row smallest elements).
%Y A381398 Cf. A035306, A381399, A381402.
%K A381398 nonn,tabf,easy
%O A381398 2,2
%A A381398 _Paolo Xausa_, Feb 22 2025