From f9c8c04e36aaedacaeafc77e1876fc23aa2f9712 Mon Sep 17 00:00:00 2001
From: Mark <53903062+andemark@users.noreply.github.com>
Date: Mon, 10 Jan 2022 11:58:34 +0000
Subject: initial 147

---
 challenge-147/mark-anderson/raku/ch-1.raku | 19 +++++++++++++++++++
 challenge-147/mark-anderson/raku/ch-2.raku | 24 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 challenge-147/mark-anderson/raku/ch-1.raku
 create mode 100644 challenge-147/mark-anderson/raku/ch-2.raku

(limited to 'challenge-147')

diff --git a/challenge-147/mark-anderson/raku/ch-1.raku b/challenge-147/mark-anderson/raku/ch-1.raku
new file mode 100644
index 0000000000..5780420a53
--- /dev/null
+++ b/challenge-147/mark-anderson/raku/ch-1.raku
@@ -0,0 +1,19 @@
+#!/usr/bin/env raku
+
+say (1, 2, 3, { $_ + 2 } ... *).grep(&tp).head(20);
+
+multi tp(\n where *.index: 0)
+{
+    return False;
+}
+
+multi tp(\n where * < 10)
+{
+    return n.is-prime
+}
+
+multi tp(\n)
+{
+    return False unless n.is-prime;
+    samewith(n.substr: 1);  
+}
diff --git a/challenge-147/mark-anderson/raku/ch-2.raku b/challenge-147/mark-anderson/raku/ch-2.raku
new file mode 100644
index 0000000000..d7581ebace
--- /dev/null
+++ b/challenge-147/mark-anderson/raku/ch-2.raku
@@ -0,0 +1,24 @@
+#!/usr/bin/env raku
+
+# Through trial and error I came up with the ~2200 figure.
+
+my @p = reverse (1..2200).map(&pentagonal);
+
+for @p X @p
+{
+    if is-pentagonal(.head + .tail) and is-pentagonal(abs(.head - .tail))
+    {
+        say .head ~ ", " ~ .tail;
+        last;
+    }
+}
+
+sub pentagonal(\n)
+{
+    n * (3 * n - 1) / 2
+}
+
+sub is-pentagonal(\n)
+{
+    return (((sqrt(24 * n + 1)) + 1) / 6).narrow ~~ UInt;
+}
-- 
cgit