A coefficient of the Maclaurin series of 1/(ln(1 + x)) = 1/x + 1/2 - 1/12 x + 1/24 x^2 - 19/720 x^3 + 3/160 x^4 + ... (OEIS A002206 and A002207), the multiplicative inverse of the Mercator series function ln(1 + x).

Mercator series