2a:null 2b:["$","title",null,{"children":"Palindrome Age checker | Job van der Zwan | Observable"}] 30:[] 2e:{"id":"d16876e2ec6519b6","slug":"palindrome-age-checker","title":"Palindrome Age checker","thumbnail":"485c00ce7db8aad445303ee599ce3621cf09c9cfa18d94d5e429fe4edfa31e83","access_level":"public","create_time":"$D2026-07-23T08:24:48.601Z","update_time":"$D2026-07-24T12:45:21.072Z","view_time":null,"first_public_time":"$D2026-07-23T09:49:48.400Z","has_unpublished_edits":null,"fork":false,"stars":1,"starred":false,"owner":{"type":"team","id":"3f83172cfde1e56a","login":"jobleonard","name":"Job van der Zwan","avatar_url":"https://avatars-next.observableusercontent.com/808373580aa09723ceabb9cb31d01ea6db287280b59eaa63618e259f5d28dd71","tier":"starter_2024"},"version":108,"publish_version":108,"role":null,"authored":false,"authors":[{"type":"individual","id":"d36034ddfb454bdd","login":"jobleonard","name":"Job van der Zwan","avatar_url":"https://avatars-next.observableusercontent.com/808373580aa09723ceabb9cb31d01ea6db287280b59eaa63618e259f5d28dd71","tier":null}],"members":[{"type":"team","id":"3f83172cfde1e56a","login":"jobleonard","name":"Job van der Zwan","avatar_url":"https://avatars-next.observableusercontent.com/808373580aa09723ceabb9cb31d01ea6db287280b59eaa63618e259f5d28dd71","tier":"starter_2024","role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"titling":"auto","title":"Palindrome Age checker","cells":[{"id":4,"value":"# Palindrome Age checker\n\nI just watched [the numberphile video on Palindrome Ages](https://www.youtube.com/watch?v=fwLsCgibGw4) (and [the extra footage](https://www.youtube.com/watch?v=bIbTfdbQaSE)) and wanted to make a simple tool to make it easy to check palindrome ages for people in different bases.\n\n\n\n","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":6,"value":"const a = view(Inputs.range([0, 120], {label: \"Person A\", value: 62, step: 1}));\nconst b = view(Inputs.range([0, 120], {label: \"Person B\", value: 26, step: 1}));\nconst maxAge = view(Inputs.range([120, 1000], {label: \"Max age to check\", value: 120, step: 1}))","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":7,"value":"const sortedAB = a < b ? [a, b] : [b, a];\nconst ageGap = sortedAB[1] - sortedAB[0];\n\nfor (let base = 2; base < 64; base++) {\n const data = [];\n for (let a = 0, b = ageGap; b < maxAge; a++, b++) {\n let bStr = toString(b, base);\n let aStr = toString(a, base, bStr.length);\n // I know there's clever maths in the videos, but I'm just brute forcing it\n const aStrReverse = aStr.split(\"\").reverse().join(\"\");\n const isPalindrome = bStr === aStrReverse;\n if (isPalindrome) {\n if (base !== 10) {\n bStr += ` (${b.toString(10)})`;\n aStr += ` (${a.toString(10)})`;\n }\n data.push({\"Person A age\": aStr, \"Person B age\": bStr});\n }\n }\n if (data.length) {\n display(html`

Palindromes for base ${base}`);\n display(Inputs.table(data))\n }\n}\n","pinned":true,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"// Note: the reason this is not in the usual order for Base64\n// is to make it match Number.toString() up to base 36.\nconst base64 = \"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/\".split(\"\")\nfunction toString(n, base = 10, minLength = 0) {\n if (n >= 0 && base >= 2 && base < base64.length && (n | 0) === n && (base | 0) === base) {\n if (base < 36) return n.toString(base).padStart(minLength, \"0\");\n else if (n === 0) return \"\".padStart(minLength, \"0\");\n let output = \"\";\n while (n) {\n const digit = n % base;\n output = base64[digit] + output;\n n = ((n - digit) / base);\n }\n while (output.length < minLength) {\n output = base64[0] + output;\n }\n return output;\n }\n}","pinned":true,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W30","stdlib":"2"}} 2f:"$2e:body"