A316842 - OEIS

%I #27 Aug 01 2019 04:08:45

%S 1,1,1,2,2,1,3,2,2,3,3,1,3,3,2,4,3,2,4,3,3,4,4,1,4,4,3,5,3,3,5,4,2,5,

%T 4,3,5,4,4,5,5,1,5,5,2,5,5,3,5,5,4,6,4,3,6,5,2,6,5,3,6,5,4,6,5,5,6,6,

%U 1,6,6,5,7,4,4,7,5,3,7,5,4,7,5,5,7,6,2,7,6,3,7,6,4,7,6,5,7,6,6,7,7,1,7,7,2,7,7,3,7,7,4,7,7,5,7,7,6,8,5,4

%N Three-column table read by rows giving primitive integer sides of proper triangles (i,j,k) with i >= j >= k >= 1, j+k > i, gcd(i,j,k) = 1.

%H Lars Blomberg, <a href="/A316842/b316842.txt">Table of n, a(n) for n = 1..9000</a>

%e Table begins:

%e [1,1,1],

%e [2,2,1],

%e [3,2,2],

%e [3,3,1],

%e [3,3,2],

%e [4,3,2],

%e [4,3,3],

%e [4,4,1],

%e [4,4,3],

%e [5,3,3],

%e [5,4,2],

%e ...

%Y There are A123323(k) rows that begin with k.

%Y The three columns are A316846, A316847, A316848.

%Y A316850 is a compressed version.

%Y See A316841 for all triples (including imprimitive triples).

%Y See A316852 and A317181 & A317183 for perimeter and area.

%Y Other related sequences: A051493, A070080, A070081, A070082, A070110.

%K nonn,tabf,look

%O 1,4

%A _N. J. A. Sloane_, Jul 23 2018, following a suggestion from _Donald S. McDonald_