Merge pull request #5498 from andemark/branch-for-challenge-147

Branch for challenge 147

2 files changed, 43 insertions, 0 deletions

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..e4dc7996fc
--- /dev/null
+++ b/challenge-147/mark-anderson/raku/ch-1.raku
@@ -0,0 +1,19 @@
+#!/usr/bin/env raku
+
+say (2, 3, { $_ + 2 } ... *).grep(&tp).head(20);
+
+multi tp(\n where *.index: 0)
+{
+    False
+}
+
+multi tp(\n where * < 10)
+{
+    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..e81d6177a0
--- /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 = (2200...1).map(&pentagonal);
+
+for @p.combinations: 2
+{
+    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)
+{
+    ((sqrt(24 * n + 1) + 1) / 6).narrow ~~ UInt
+}