Wagstaff primes: Difference between revisions

Content added Content deleted

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@@ Line 217: / Line 217: @@
 var isWagstaff = Fn.new { |p|
-    var w = (2.pow(p) + 1) / 3
+    var w = (2.pow(p) + 1) / 3  // always integral
-    if (!w.isInteger || !Int.isPrime(w)) return [false, null]
+    if (!Int.isPrime(w)) return [false, null]
     return [true, [p, w]]
 }
 var isBigWagstaff = Fn.new { |p|
-    var w = Mpz.one.lsh(p).add(1)
+    var w = Mpz.one.lsh(p).add(1).div(3)
-    if (!w.isDivisibleUi(3)) return [false, null]
+    return w.probPrime(15) > 0
-    w.div(3)
-    if (w.probPrime(15) == 0) return [false, null]
-    return [true, p]
 }
@@ Line 254: / Line 251: @@
         if (Int.isPrime(p)) break
     }
-    var res = isBigWagstaff.call(p)
+    if (isBigWagstaff.call(p)) {
+        Fmt.print("$5d ($3d secs)", p, (System.clock - start).ceil)
-    if (res[0]) {
-        Fmt.print("$5d ($3d secs)", res[1], (System.clock - start).ceil)
         count = count + 1
     }
@@ Line 275: / Line 271: @@
 : 2932031007403
-Took 0.056335 seconds
+Took 0.055678 seconds
 Values of 'p' for the next 19 Wagstaff primes and
@@ Line 293: / Line 289: @@
 (  5 secs)
 ( 25 secs)
-(198 secs)
+(193 secs)
-(210 secs)
+(205 secs)
-(251 secs)
+(244 secs)
-(348 secs)
+(341 secs)
-(599 secs)
+(593 secs)
 </pre>