# HG changeset patch
# User Steve Losh <steve@stevelosh.com>
# Date 1487786910 0
# Node ID d2de8990952fb9b646e05d3b5d8e15fbfafd2d07
# Parent  81710e614e2147c37ff9610b383ece41df137d39
Problem 29

diff -r 81710e614e21 -r d2de8990952f src/euler.lisp
--- a/src/euler.lisp	Wed Feb 22 18:01:30 2017 +0000
+++ b/src/euler.lisp	Wed Feb 22 18:08:30 2017 +0000
@@ -825,6 +825,25 @@
        ;; don't double-count the center...
        (- (aref spiral (truncate size 2) (truncate size 2))))))
 
+(defun problem-29 ()
+  ;; Consider all integer combinations of a^b for 2 ≤ a ≤ 5 and 2 ≤ b ≤ 5:
+  ;;
+  ;; 2²=4,  2³=8,   2⁴=16,  2⁵=32
+  ;; 3²=9,  3³=27,  3⁴=81,  3⁵=243
+  ;; 4²=16, 4³=64,  4⁴=256, 4⁵=1024
+  ;; 5²=25, 5³=125, 5⁴=625, 5⁵=3125
+  ;;
+  ;; If they are then placed in numerical order, with any repeats removed, we
+  ;; get the following sequence of 15 distinct terms:
+  ;;
+  ;; 4, 8, 9, 16, 25, 27, 32, 64, 81, 125, 243, 256, 625, 1024, 3125
+  ;;
+  ;; How many distinct terms are in the sequence generated by a^b for
+  ;; 2 ≤ a ≤ 100 and 2 ≤ b ≤ 100?
+  (length (iterate (for-nested ((a :from 2 :to 100)
+                                (b :from 2 :to 100)))
+                   (adjoining (expt a b)))))
+
 
 ;;;; Tests --------------------------------------------------------------------
 (def-suite :euler)
@@ -858,6 +877,7 @@
 (test p26 (is (= 983 (problem-26))))
 (test p27 (is (= -59231 (problem-27))))
 (test p28 (is (= 669171001 (problem-28))))
+(test p29 (is (= 9183 (problem-29))))
 
 
 ;; (run! :euler)