/*
Copyright (C) 2019 D.H.J. Polymath
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "fmpz.h"
#include "acb_dirichlet.h"
slong
acb_dirichlet_backlund_s_gram(const fmpz_t n)
{
slong res = 0;
if (fmpz_cmp_si(n, -1) < 0)
{
flint_throw(FLINT_ERROR, "n must be >= -1\n");
}
else
{
fmpz_t k;
fmpz_init(k);
acb_dirichlet_zeta_nzeros_gram(k, n);
fmpz_sub(k, k, n);
res = fmpz_get_si(k) - 1;
fmpz_clear(k);
}
return res;
}