Knowing a sequence of moments of a given, infinitely supported, distribution
we obtain quickly: coefficients of the power series expansion of monic
polynomials $\left\{ p_{n}\right\} _{n\geq 0}$ that are orthogonal with respect
to this distribution, coefficients of expansion of $x^{n}$ in the series of
$p_{j},$ $j\leq n$, two sequences of coefficients of the 3-term recurrence of
the family of $\left\{ p_{n}\right\} _{n\geq 0}$, the so called "linearization
coefficients" i.e. coefficients of expansion of $% p_{n}p_{m}$ in the series of
$p_{j},$ $j\leq m+n.$\newline Conversely, assuming knowledge of the two
sequences of coefficients of the 3-term recurrence of a given family of
orthogonal polynomials $\left\{ p_{n}\right\} _{n\geq 0},$ we express with
their help: coefficients of the power series expansion of $p_{n}$, coefficients
of expansion of $x^{n}$ in the series of $p_{j},$ $j\leq n,$ moments of the
distribution that makes polynomials $\left\{ p_{n}\right\} _{n\geq 0}$
orthogonal. \newline Further having two different families of orthogonal
polynomials $\left\{ p_{n}\right\} _{n\geq 0}$ and $\left\{ q_{n}\right\}
_{n\geq 0}$ and knowing for each of them sequences of the 3-term recurrences,
we give sequence of the so called "connection coefficients" between these two
families of polynomials. That is coefficients of the expansions of $p_{n}$ in
the series of $q_{j},$ $j\leq n.$\newline We are able to do all this due to
special approach in which we treat vector of orthogonal polynomials $\left\{
p_{j}\left( x)\right) \right\} _{j=0}^{n}$ as a linear transformation of the
vector $\left\{ x^{j}\right\} _{j=0}^{n}$ by some lower triangular $(n+1)\times
(n+1)$ matrix $\mathbf{\Pi }_{n}.$Comment: 18 page