2025 is a good number, it’s a quarter of the way through the 20 hundreds and it’s got that nice set of 2s separated by only a 0. not bad. whatever happens this year at least it’ll be happening during a good number 😌
and IT’S A SQUARE. IT’S 45 SQUARED. THE LAST TIME THIS HAPPENED WAS IN 1936 (44 squared) AND IT WON’T HAPPEN AGAIN UNTIL 2116 (46 squared)
It’s not just any square, it’s the square of a triangle number – 45 = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9. (Which is also the sum of all the squares in a Sudoku grid, an inescapable tool if you like to do more mathematically intense sudokus.)
The squares of triangle numbers, also known as Nicomachus numbers, have a very interesting identity – the square of the sum is equal to the sum of the cubes! So we have
The previous Nicomachus year was 1296, and the next is 3025 – and given that the Gregorian calendar wasn’t in use until the 16th century, I’m not holding my breath for a second Gregorian Nicomachus year to happen at all.
amhrancas 