One Is The Loneliest Number Paul Williams, Three Dog Night (#5 in 1969)

One is the loneliest number that you'll ever do
Two can be as bad as one
It's the loneliest number since the number one

"No" is the saddest experience you'll ever know
Yes, it's the saddest experience you'll ever know
'Cause one is the loneliest number that you'll ever do
One is the loneliest number, whoa, worse than two
 
It's just no good anymore since you went away
Now I spend my time just making rhymes of yesterday
One is the loneliest number
One is the loneliest number
One is the loneliest number that you'll ever do
One is the loneliest, one is the loneliest
One is the loneliest number that you'll ever do
 
It's just no good anymore since you went away
 
Number One is the loneliest
Number One is the loneliest
Number One is the loneliest number that you'll ever do
(Repeat in various forms)