Linear OA(256³³, 780, F₂₅₆, 19) (dual of [780, 747, 20]-code), using 509 step VarÅ¡amov–Edel lengthening with (r_i) = (7, 1, 0, 0, 1, 9 times 0, 1, 20 times 0, 1, 44 times 0, 1, 85 times 0, 1, 140 times 0, 1, 201 times 0) based on linear OA(256¹⁹, 257, F₂₅₆, 19) (dual of [257, 238, 20]-code or 257-arc in PG(18,256)), using

• extended Reed–Solomon code RS_e(238,256) [i]
• the expurgated narrow-sense BCH-code C(I) with length 257 | 256²âˆ’1, defining interval I = [0,9], and minimum distance d ≥ |{−9,−8,…,9}|+1 = 20 (BCH-bound) [i]
• algebraic-geometric code AG(F, Q+117P) with degQ = 3 and degP = 2 [i] based on function field F/F₂₅₆ with g(F) = 0 and N(F) ≥ 257, using the rational function field F₂₅₆(x) [i]
• algebraic-geometric code AG(F,79P) with degP = 3 [i] based on function field F/F₂₅₆ with g(F) = 0 and N(F) ≥ 257 (see above)
• algebraic-geometric code AG(F, Q+47P) with degQ = 2 and degP = 5 [i] based on function field F/F₂₅₆ with g(F) = 0 and N(F) ≥ 257 (see above)