LogIntegral[z] is the logarithmic integral function li(z).
LogitModelFit[{y_1, y_2, ...}, {f_1, f_2, ...}, x] constructs a binomial logistic regression model of the form 1/(1 + E -(\[Beta]_0 + \[Beta]_1 f_1 + \[Beta]_2 f_2 + \ ...)) ...
ModularLambda[\[Tau]] gives the modular lambda elliptic function \[Lambda](\[Tau]).
NorlundB[n, a] gives Nørlund polynomials B_n^(a) of degree n in a.NorlundB[n, a, x] gives generalized Bernoulli polynomials B_n^(a)(x).
Or
(Built-in Mathematica Symbol) e_1 || e_2 || ... is the logical OR function. It evaluates its arguments in order, giving True immediately if any of them are True, and False if they are all False.
ProbitModelFit[{y_1, y_2, ...}, {f_1, f_2, ...}, x] constructs a binomial probit regression model of the form 1/2 (1 + erf((\[Beta]_0 + \[Beta]_1 f_1 + \[Beta]_2 f_2 + \ ...
RiemannSiegelTheta[t] gives the Riemann\[Dash]Siegel function \[CurlyTheta](t).
RiemannSiegelZ[t] gives the Riemann\[Dash]Siegel function Z(t).
SinhIntegral[z] gives the hyperbolic sine integral function Shi(z).
SixJSymbol[{j_1, j_2, j_3}, {j_4, j_5, j_6}] gives the values of the Racah 6-j symbol.