Вы можете использовать преобразование:
table {
font-family: verdana, arial, sans-serif;
font-size: 11px;
color: #333333;
border-width: 1px;
border-color: #3A3A3A;
border-collapse: collapse;
}
table th {
border-width: 1px;
padding: 8px;
border-style: solid;
border-color: #3A3A3A;
background-color: #B3B3B3;
}
table td {
border-width: 1px;
padding: 8px;
border-style: solid;
border-color: #3A3A3A;
background-color: #ffffff;
}
:empty {
opacity:0;
}
tbody tr td:nth-child(even) {
transform: translateY(-50%);
box-shadow:0 0 0 1px #3a3a3a
}
<table>
<thead>
<tr>
<th>boundary</th>
<th>slice</th>
<th>h_i</th>
<th>1/2 (h_{i+1}+h_i)</th>
</tr>
</thead>
<tbody>
<tr>
<td>0</td>
<td></td>
<td>0.00</td>
<td></td>
</tr>
<tr>
<td>1</td>
<td>1</td>
<td>2.26</td>
<td>1.13</td>
</tr>
<tr>
<td>2</td>
<td>2</td>
<td>4.37</td>
<td>3.32</td>
</tr>
<tr>
<td>3</td>
<td>3</td>
<td>6.32</td>
<td>5.35</td>
</tr>
<tr>
<td>4</td>
<td>4</td>
<td>5.74</td>
<td>6.03</td>
</tr>
<tr>
<td>5</td>
<td>5</td>
<td>4.90</td>
<td>5.32</td>
</tr>
<tr>
<td>6</td>
<td>6</td>
<td>3.61</td>
<td>4.25</td>
</tr>
<tr>
<td>7</td>
<td>7</td>
<td>0.00</td>
<td>1.80</td>
</tr>
</tbody>
</table>
Иначе, без CSS, используйте также атрибут rowspan и пустые ячейки в последней строке.
td:empty {
opacity: 0;
}
table {
font-family: verdana, arial, sans-serif;
font-size: 11px;
color: #333333;
border-width: 1px;
border-color: #3A3A3A;
border-collapse: collapse;
}
table th {
border-width: 1px;
padding: 8px;
border-style: solid;
border-color: #3A3A3A;
background-color: #B3B3B3;
}
table td {
border-width: 1px;
padding: 8px;
border-style: solid;
border-color: #3A3A3A;
background-color: #ffffff;
}
:empty {
opacity: 0;
}
<table>
<thead>
<tr>
<th>boundary</th>
<th>slice</th>
<th>h_i</th>
<th>1/2 (h_{i+1}+h_i)</th>
</tr>
</thead>
<tbody>
<tr>
<td rowspan=2>0</td>
<td></td>
<td rowspan=2>0.00</td>
<td></td>
</tr>
<tr>
<td rowspan=2>1</td>
<td rowspan=2>2.26</td>
</tr>
<tr>
<td rowspan=2>1</td>
<td rowspan=2>1.13</td>
</tr>
<tr>
<td rowspan=2>2</td>
<td rowspan=2>4.37</td>
</tr>
<tr>
<td rowspan=2>2</td>
<td rowspan=2>3.32</td>
</tr>
<tr>
<td rowspan=2>3</td>
<td rowspan=2>6.32</td>
</tr>
<tr>
<td rowspan=2>3</td>
<td rowspan=2>5.35</td>
</tr>
<tr>
<td rowspan=2>4</td>
<td rowspan=2>5.74</td>
</tr>
<tr>
<td rowspan=2>4</td>
<td rowspan=2>6.03</td>
</tr>
<tr>
<td rowspan=2>5</td>
<td rowspan=2>4.90</td>
</tr>
<tr>
<td rowspan=2>5</td>
<td rowspan=2>5.32</td>
</tr>
<tr>
<td rowspan=2>6</td>
<td rowspan=2>3.61</td>
</tr>
<tr>
<td rowspan=2>6</td>
<td rowspan=2>4.25</td>
</tr>
<tr>
<td rowspan=2>7</td>
<td rowspan=2>0.00</td>
</tr>
<tr>
<td rowspan=2>7</td>
<td rowspan=2>1.80</td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
</tbody>
</table>
https://html.com/tables/rowspan-colspan/