### Sophie Germain Primes and Cunningham Chains

A Sophie Germain prime is a prime number such that is also a prime number. That is, ,  where and are both prime.  For example, . The sequence begins Sophie Germain () explored these primes [more…]

### The Infinity of the Primes

Euclid’s Elements, Book IX, Proposition 20. Theorem : Prime numbers are more than any assigned multitude of prime numbers. That is, there are infinitely many primes. Proof : Suppose that there are primes : Let [more…]

### The Number of Derangements

Read as : the limit, as approaches infinity, of subfactorial divided by factorial is equal to divided by which approximates to , where is Euler’s number, The Hat Check Problem, as first described by Montmort [more…]

### On Punctuation!

Apparently, some subset of younger people are upset and intimidated about the use of full stops in text and other messages. I am not sure what they would think about the ellipsis, … , or [more…]

### From a Sum to a Product

In The Basel Problem we saw that Euler answered the question by showing that the sum of the reciprocals of the square numbers is equal to . That is The partial sums slowly converge to [more…]

### Vanilla Ice Cream Terrine with Ginger, Chocolate and Salted Caramel

1 litre vanilla ice cream 100g stem ginger biscuits/cookies 100g dark chocolate 125g salted caramel cream sauce You can buy salted caramel cream sauce or make your own in ten minutes. To make your own [more…]

### Hark! The Herald Angels Sing

Painted in about 1470/75, it is in the National Gallery. One of my favourite carols: Merry Christmas!   OldTrout 2019

### The Holly and the Ivy

The words of the carol occur in three broadsides published in Birmingham in the early nineteenth century. An early mention of the carol’s title occurs in William Hone’s 1823 work Ancient Mysteries Described, which includes [more…]

### The Coventry Carol

The fourth Sunday of Advent. #Love Original spelling Modernised spelling Lully, lulla, thow littell tine child, By by, lully, lullay thow littell tyne child, By by, lully, lullay! Lully, lullay, thou little tiny child, Bye [more…]