ARSE

Thu 28 Oct 2021

Hexagonal Days

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Find out when you will be celebrating!

Hexagonal Days occur when your day age is a centred hexagonal number.

A centred hexagonal number, or hex number, is a centred figurate number that represents a hexagon with a dot in the centre and all other dots surrounding the centre dot in a hexagonal lattice.

Strictly, a hexagonal number is the number of distinct dots in a pattern of dots consisting of the *outlines* of regular hexagons with sides up to *n* dots, when the hexagons are overlaid so that they share one vertex.

We choose to use *centred* hexagonal numbers to calculate our Hexagonal Days because all (outlined) hexagonal numbers are also triangular numbers and these are already commemorated in our Triangular Days.

Centred Hexagonal

1

7

19

37

61

91

Hexagonal

1

6

15

28

45

66

91

Triangular

1

3

6

10

15

21

28

36

45

55

66

78

91