> A:= Matrix(12, 12, [
>    [0,0,0,0,0,0,0,0,0,0,0,0],
>    [4/9,0,0,0,0,0,0,0,0,0,0,0],
>    [1/6,1/2,0,0,0,0,0,0,0,0,0,0],
>    [2743/15972,845/2662,-507/5324,0,0,0,0,0,0,0,0,0],
>    [249/1664,0,21/128,363/832,0,0,0,0,0,0,0,0],
>    [43/351,0,-79/162,847/2106,8/27,0,0,0,0,0,0,0],
>    [5182/40625,0,-8243/18750,147983/243750,792/3125,-1089/3125,0,0,0,0,0,0],
>    [1940561/31200000,0,1989631/2400000,-16400461/31200000,-7903/18750,386001/800000,35/128,0,0,0,0,0],
>    [-135846/3128125,0,86049/68750,-120879/81250,-288648/378125,369441/378125,348/605,384/4235,0,0,0,0],
>    [1551679/5362500,0,-325991/412500,773311/487500,-379264/1134375,44919/1512500,-161/242,224/121,-7/6,0,0,0],
>    [-187113/557375,0,12413/5250,-325853/68250,1352/375,1625796/471625,52/49,-14464/3773,110/147,-440/343,0,0],
>    [589/10584,0,0,0,26624/10395,-13851/172480,15325/44352,-13600/4851,15125/12096,-1375/3528,35/576,0]
> ]):
> evalm(A);

> Matrix(12, 12, [
>  [0,0,0,0,0,0,0,0,0,0,0,0],
>  [4/9,0,0,0,0,0,0,0,0,0,0,0],
>  [1/6,1/2,0,0,0,0,0,0,0,0,0,0],
>  [2743/15972,845/2662,-507/5324,0,0,0,0,0,0,0,0,0],
>  [249/1664,0,21/128,363/832,0,0,0,0,0,0,0,0],
>  [43/351,0,-79/162,847/2106,8/27,0,0,0,0,0,0,0],
>  [5182/40625,0,-8243/18750,147983/243750,792/3125,-1089/3125,0,0,0,0,0,0],
>  [1940561/31200000,0,1989631/2400000,-16400461/31200000,-7903/18750,386001/800000,35/128,0,0,0,0,0],
>  [-135846/3128125,0,86049/68750,-120879/81250,-288648/378125,369441/378125,348/605,384/4235,0,0,0,0],
>  [-43223/768768,0,6305/8448,-11737/9984,-43/3630,78453/154880,10775/15488,-725/847,125/192,0,0,0],
>  [-42587/75335,0,97073/34770,-2336873/452010,62408/38247,37062/63745,35400/12749,-54400/12749,2750/3477,2816/1159,0,0],
>  [52/945,0,0,0,65536/51975,-16767/123200,15875/44352,-1000/693,6875/12096,88/315,1159/20160,0]
> ]):
> evalm(A);