Landau–Ramanujan_constant
In mathematics and the field of number theory, the Landau–Ramanujan constant is the positive real number b that occurs in a theorem proved by Edmund Landau in 1908,[1] stating that for large , the number of positive integers below that are the sum of two square numbers behaves asymptotically as
This constant b was rediscovered in 1913 by Srinivasa Ramanujan, in the first letter he wrote to G.H. Hardy.[2]