NAME
    euler - Euler number

SYNOPSIS
    euler(n)

TYPES
    n		integer, n <= 1000000 if even

    return	integer

DESCRIPTION
    Returns the Euler number with index n, i.e. the coefficient E_n in
    the expansion

		sech(t) = Sigma E_n * t^n/n!

    When euler(n) is computed for positive even n, the values for
    n and smaller positive even indices are stored in a table so that
    a later call to euler(k) with 0 <= k <= n will be executed quickly.
    If euler(k) is called with negative k, zero is returned and the
    memory used by the table iu freed.

    Considerable runtime and memery are required for calculating
    euler(n) for large even n.

EXAMPLE
    > for (n = 0; n <= 6; n++) print euler(n),; print;
    1 0 -1 0 5 0 -61

LIMITS
    none

LINK LIBRARY
    NUMBER *qeuler(long n)

SEE ALSO
    bernoulli, bell, catalan, comb, fact, perm