In 2010 I was working in a bookshop and teaching myself the web scripting language PHP. A good way to learn a language is to find problems you can solve with it, and as I had recently been working with ISBNs, the identifying numbers given to printed books, I decided to write a program to search Pi for them.<\/p>\n
I found the first three books in Pi<\/a>. Then, a few years later, it got picked up by a few popular Twitter accounts and went viral, including a write-up in the science page of Der Spiegel<\/a>.<\/p>\n What’s the point? There isn’t, other than a programming exercise and the pleasure of finding things out. But it does raise a few interesting things:<\/p>\n Normal in this sense means “does it have the same numbers of each digit, 0-9?” As you’d expect, there’s about a thousand times more ISBNs if you search for the 10 digit version, as it’s a shorter string and more likely to appear in any random set of digits. Some ISBN-10s end in an X, which obviously doesn’t appear in Pi, but that can be ignored, we’re just messing about here. David J Fianders went to the effort of tracking down ISBN-10s<\/a>.<\/p>\n ISBNs are constantly being added for new publications, so it may well be that “my” first three books have been superseded. Feel free to try searching for new ones!<\/p>\n","protected":false},"excerpt":{"rendered":" In 2010 I was working in a bookshop and teaching myself the web scripting language PHP. A good way to learn a language is to find problems you can solve with it, and as I had recently been working with ISBNs, the identifying numbers given to printed books, I decided to write a program to […]<\/p>\n","protected":false},"author":1,"featured_media":61,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,3],"tags":[],"_links":{"self":[{"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/posts\/60"}],"collection":[{"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/comments?post=60"}],"version-history":[{"count":3,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/posts\/60\/revisions"}],"predecessor-version":[{"id":64,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/posts\/60\/revisions\/64"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/media\/61"}],"wp:attachment":[{"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/media?parent=60"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/categories?post=60"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thegeoff.net\/gr-wp\/wp-json\/wp\/v2\/tags?post=60"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Is Pi “normal”?<\/h4>\n
\nIf Pi is<\/em> normal then you’d expect every possible number sequence to appear in it. If it’s not (say, if you get to a certain point and then there’s never a 9 again) then it won’t. It’s generally thought that Pi is<\/em> normal, but it’s still an open question in mathematics.<\/p>\nHow does it fare with the old 10 digit ISBN?<\/h4>\n
It’s now out of date!<\/h4>\n