Table:
0
A
B
C
D
E
1
District
Vacator
Reason for change
Successor
Date successor seated
2
Pennsylvania 4th
John A. Hanna (DR)
Died July 23, 1805
Robert Whitehill (DR)
Seated November 7, 1805
3
Georgia At-large
Cowles Mead (DR)
Lost contested election December 24, 1805
Thomas Spalding (DR)
Seated December 24, 1805
4
Georgia At-large
Joseph Bryan (DR)
Resigned sometime in 1806
Dennis Smelt (DR)
September 1, 1806
5
Georgia At-large
Thomas Spalding (DR)
Resigned sometime in 1806
William W. Bibb (DR)
Seated January 26, 1807
6
Pennsylvania 1st
Michael Leib (DR)
Resigned February 14, 1806
John Porter (DR)
Seated December 8, 1806
7
Maryland 7th
Joseph H. Nicholson (DR)
Resigned March 1, 1806
Edward Lloyd (DR)
Seated December 3, 1806
8
Virginia 13th
Christopher H. Clark (DR)
Resigned July 1, 1806
William A. Burwell (DR)
December 1, 1806
9
Connecticut At-large
John Cotton Smith (F)
Resigned sometime in August, 1806
Theodore Dwight (F)
December 1, 1806
10
Pennsylvania 3rd
Christian Lower (DR)
Resigned December 19, 1806
Vacant
Not filled for remainder of term

Questions and formulas:
Question: Who left a seat open for the district of connecticut at-large
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Connecticut At-large"),2))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E10,A2:A10="Connecticut At-large"),2))
Level: medium
Question: Why was a seat left open fo Connecticut at-large?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Connecticut At-large"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E10,A2:A10="Connecticut At-large"),3))
Level: medium