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/*
Copyright (C) 2011 Fredrik Johansson
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_vec.h"
#include "fmpz_poly.h"
#include "arith.h"
void
arith_number_of_partitions_vec(fmpz * res, slong len)
{
fmpz * tmp;
slong k, n;
if (len < 1)
return;
tmp = _fmpz_vec_init(len);
tmp[0] = WORD(1);
for (n = k = 1; n + 4*k + 2 < len; k += 2)
{
tmp[n] = WORD(-1);
tmp[n + k] = WORD(-1);
tmp[n + 3*k + 1] = WORD(1);
tmp[n + 4*k + 2] = WORD(1);
n += 6*k + 5;
}
if (n < len) tmp[n] = WORD(-1);
if (n + k < len) tmp[n + k] = WORD(-1);
if (n + 3*k + 1 < len) tmp[n + 3*k + 1] = WORD(1);
_fmpz_poly_inv_series(res, tmp, len, len);
_fmpz_vec_clear(tmp, len);
}