a_{1}, a_{1} + d, a_{1} + 2 d, a_{1} + 3 d, \dots

${a_1,a_1 + d,a_1 + 2d,a_1 + 3d, \ldots}$

a_{1}, a_{1} + d, a_{1} + 2 d, a_{1} + 3 d, \dots

$a_1,a_1 + d,a_1 + 2d,a_1 + 3d, \ldots$

a_{1}

$a_1$

a_{1}

$a_1$

1

d

$d$

1

\dots

$\ldots$

1

Lisa

OK

Error