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diff --git a/gmp/mpz/lucnum2_ui.c b/gmp/mpz/lucnum2_ui.c
new file mode 100644
index 00000000..a6b6cfb6
--- /dev/null
+++ b/gmp/mpz/lucnum2_ui.c
@@ -0,0 +1,81 @@
+/* mpz_lucnum2_ui -- calculate Lucas numbers.
+
+Copyright 2001, 2003, 2005 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
+
+#include <stdio.h>
+#include "gmp.h"
+#include "gmp-impl.h"
+
+
+void
+mpz_lucnum2_ui (mpz_ptr ln, mpz_ptr lnsub1, unsigned long n)
+{
+  mp_ptr     lp, l1p, f1p;
+  mp_size_t  size;
+  mp_limb_t  c;
+  TMP_DECL;
+
+  ASSERT (ln != lnsub1);
+
+  /* handle small n quickly, and hide the special case for L[-1]=-1 */
+  if (n <= FIB_TABLE_LUCNUM_LIMIT)
+    {
+      mp_limb_t  f  = FIB_TABLE (n);
+      mp_limb_t  f1 = FIB_TABLE ((int) n - 1);
+
+      /* L[n] = F[n] + 2F[n-1] */
+      PTR(ln)[0] = f + 2*f1;
+      SIZ(ln) = 1;
+
+      /* L[n-1] = 2F[n] - F[n-1], but allow for L[-1]=-1 */
+      PTR(lnsub1)[0] = (n == 0 ? 1 : 2*f - f1);
+      SIZ(lnsub1) = (n == 0 ? -1 : 1);
+
+      return;
+    }
+
+  TMP_MARK;
+  size = MPN_FIB2_SIZE (n);
+  f1p = TMP_ALLOC_LIMBS (size);
+
+  MPZ_REALLOC (ln,     size+1);
+  MPZ_REALLOC (lnsub1, size+1);
+  lp  = PTR(ln);
+  l1p = PTR(lnsub1);
+
+  size = mpn_fib2_ui (l1p, f1p, n);
+
+  /* L[n] = F[n] + 2F[n-1] */
+#if HAVE_NATIVE_mpn_addlsh1_n
+  c = mpn_addlsh1_n (lp, l1p, f1p, size);
+#else
+  c = mpn_lshift (lp, f1p, size, 1);
+  c += mpn_add_n (lp, lp, l1p, size);
+#endif
+  lp[size] = c;
+  SIZ(ln) = size + (c != 0);
+
+  /* L[n-1] = 2F[n] - F[n-1] */
+  c = mpn_lshift (l1p, l1p, size, 1);
+  c -= mpn_sub_n (l1p, l1p, f1p, size);
+  ASSERT ((mp_limb_signed_t) c >= 0);
+  l1p[size] = c;
+  SIZ(lnsub1) = size + (c != 0);
+
+  TMP_FREE;
+}