%I A020886
%S A020886 6,15,20,28,35,42,45,63,66,72,77,88,91,99,104,110,117,120,130,143,153,
%T A020886 156,165,170,187,190,195,204,209,210,221,228,231,238,247,255,266,272,
%U A020886 273,276,285,299,304,322,323,325,336,342,345,350,357,368,378,391,399
%N A020886 Ordered semiperimeters of primitive Pythagorean triangles.
%C A020886 n is in this sequence iff A078926(n)>0. This is a subset of A005279.
%p A020886 isA020886 := proc(an) local r::integer,s::integer ; for r from floor((an/
               2)^(1/2)) to floor(an^(1/2)) do for s from r-1 to 1 by -2 do if r*(r+s) 
               = an and gcd(r,s) < 2 then RETURN(true) ; fi ; if r*(r+s) < an then 
               break ; fi ; od ; od : RETURN(false) ; end : for n from 2 to 400 
               do if isA020886(n) then printf("%d,",n) ; fi ; od ; - R. J. Mathar 
               (mathar(AT)strw.leidenuniv.nl), Jun 08 2006
%Y A020886 Cf. A020882-A020885. a(n) = A024364(n)/2.
%Y A020886 Sequence in context: A045848 A044439 A128253 this_sequence A093508 A094183 
               A162693
%Y A020886 Adjacent sequences: A020883 A020884 A020885 this_sequence A020887 A020888 
               A020889
%K A020886 nonn
%O A020886 0,1
%A A020886 Clark Kimberling (ck6(AT)evansville.edu)