diff --git a/extra/project-euler/203/203.factor b/extra/project-euler/203/203.factor
index 2077fe328e..2c0a73c3ac 100644
--- a/extra/project-euler/203/203.factor
+++ b/extra/project-euler/203/203.factor
@@ -1,6 +1,7 @@
 ! Copyright (c) 2008 Eric Mertens.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: fry kernel math math.primes.factors sequences sets project-euler.common ;
+USING: fry kernel math math.primes.factors math.vectors sequences sets
+project-euler.common ;
 IN: project-euler.203
 
 ! http://projecteuler.net/index.php?section=problems&id=203
@@ -42,7 +43,7 @@ IN: project-euler.203
     swapd '[ @ dup ] replicate nip ; inline
 
 : (generate) ( seq -- seq )
-    [ 0 prefix ] [ 0 suffix ] bi [ + ] 2map ;
+    [ 0 prefix ] [ 0 suffix ] bi v+ ;
 
 : generate ( n -- seq )
     1 - { 1 } [ (generate) ] iterate combine ;
diff --git a/extra/project-euler/common/common.factor b/extra/project-euler/common/common.factor
index f72a5b96af..ddadd4079a 100644
--- a/extra/project-euler/common/common.factor
+++ b/extra/project-euler/common/common.factor
@@ -4,8 +4,8 @@
 USING: accessors arrays byte-arrays fry hints kernel lists make math
     math.functions math.matrices math.order math.parser math.primes.factors
     math.primes.lists math.primes.miller-rabin math.ranges math.ratios
-    namespaces parser prettyprint quotations sequences sorting strings
-    unicode.case vocabs vocabs.parser words ;
+    math.vectors namespaces parser prettyprint quotations sequences sorting
+    strings unicode.case vocabs vocabs.parser words ;
 FROM: sequences => change-nth ;
 IN: project-euler.common
 
@@ -74,7 +74,7 @@ PRIVATE>
 
 : max-path ( triangle -- n )
     dup length 1 > [
-        2 cut* first2 max-children [ + ] 2map suffix max-path
+        2 cut* first2 max-children v+ suffix max-path
     ] [
         first first
     ] if ;