The Copeland-Erdős constant is the concatenation of "0." with the base 10 representations of the prime numbers in order. Its value is approximately

0.235711131719232931374143... (sequence A33308 in the OEIS)

It is given by

where p(n) gives the n-th prime number.

The larger Smarandache-Wellin numbers approximate the value of this constant multiplied by the appropriate power of 10.

Its continued fraction is [0; 4, 4, 8, 16, 18, 5, 1, ...] (OEIS: A30168)

In base 10, this is a normal number, a fact proven by Arthur Herbert Copeland and Paul Erdős in 1946 (hence the name of the constant).