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 A020886 Ordered semiperimeters of primitive Pythagorean triangles. 27
 6, 15, 20, 28, 35, 42, 45, 63, 66, 72, 77, 88, 91, 99, 104, 110, 117, 120, 130, 143, 153, 156, 165, 170, 187, 190, 195, 204, 209, 210, 221, 228, 231, 238, 247, 255, 266, 272, 273, 276, 285, 299, 304, 322, 323, 325, 336, 342, 345, 350, 357, 368, 378, 391, 399 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n is in this sequence iff A078926(n)>0. This is a subset of A005279. LINKS FORMULA a(n) = A024364(n)/2. MAPLE 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, Jun 08 2006 CROSSREFS Cf. A020882-A020885. Sequence in context: A294651 A044439 A128253 * A093508 A302022 A094183 Adjacent sequences:  A020883 A020884 A020885 * A020887 A020888 A020889 KEYWORD nonn AUTHOR STATUS approved

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Last modified October 20 03:04 EDT 2019. Contains 328244 sequences. (Running on oeis4.)