| 词条 | 228 (number) |
| 释义 |
228 (two hundred [and] twenty-eight) is the natural number following 227 and preceding 229. {{Infobox number| number = 228 | prime = no }} 228 is a refactorable number,[1] and a practical number.[2] There are 228 matchings in a ladder graph with five rungs.[3] 228 is the smallest even number n such that the numerator of the nth Bernoulli number is divisible by a nontrivial square number that is relatively prime to n.[4] The binary form of 228 contains all the two digit binary numbers in sequence from highest to lowest (11 10 01 00). References1. ^{{Cite OEIS|A033950|name=Refactorable numbers}} {{Integers|2}}{{Num-stub}}2. ^{{Cite OEIS|A005153|name=Practical numbers}} 3. ^{{Cite OEIS|A030186|name=a(n) = 3a(n-1) + a(n-2) - a(n-3)}} 4. ^{{Cite OEIS|A090943|name=Even numbers n such that N(n) is divisible by a nontrivial square, m^2, say and GCD(n,m)=1, where N(n) is the numerator of the Bernoulli number B(n)}} 1 : Integers |
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