34.patch


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From e6258748e92f8244a144c21a67af7e3713beaac8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20=C8=98uteu?= <trizen@protonmail.com>
Date: Tue, 5 Nov 2019 16:47:38 +0200
Subject: [PATCH] Handle 2^n in is_totient()

Fixes https://github.com/danaj/Math-Prime-Util/issues/33.

See also: [A058213](https://oeis.org/A058213), [A058215](https://oeis.org/A058215).
---
 util.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/util.c b/util.c
index e03ac43..4199254 100644
--- a/util.c
+++ b/util.c
@@ -1059,6 +1059,7 @@ static int _totpred(UV n, UV maxd) {
   int res;
 
   if (n & 1) return 0;
+  if ((n & (n-1)) == 0) return 1;
   n >>= 1;
   if (n == 1) return 1;
   if (n < maxd && is_prime(2*n+1)) return 1;