Monthly Archives: December 2024

Concert Concat 2025

Published by peter on 2024-12-30 in Concats, Concert Concats, Concerts, Jazz and Music. Closed

This post is one in a sequence which lists (mostly) live music I have heard, as best as memory allows. I write to have a record of my musical experiences and so these entries are intended as postcards from me to my future self. All opinions are personal.

Other posts in this collection can be found here. The most recent prior post in this sequence is here.

  • Alexander Melnikov (piano) and Jeroen Berwaerts (trumpet) with the Australian Chamber Orchestra under Richard Tognetti in a concert of Bach, Shostakovich and Gubaidulina at The Barbican, London, Friday 21 March 2025.

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The Year 2025

Published by peter on 2024-12-30 in Mathematics. Closed

The year 2025 is a square number, since 2025 = 45 * 45. The adjacent years which are also squares are 1936 = 44 * 44 and 2116 = 46 * 46. There will be people who are alive for two of these three years, but nobody for all three (unless human lifespans increase dramatically for people born before 1937).

A Harshad number (aka a Niven number) is a number which is evenly divisible by the sum of its digits, eg, the number 24 is evenly divisible by 6, the sum of 2 + 4. The number 2025 is evenly divisible by 9 (the sum of 2 + 0 + 2 + 5), so it is a Harshad number. Likewise, the past three years are all evenly divisible by the sum of their respective digits: 2022, 2023 and 2024.

A sequence of four Harshad years in a row like this (2022, 2023, 2024, 2025) is quite rare. The last time this happened was a millenium ago, in the year 1014, and the next time it will happen will be in the year 3030, a millenium ahead of us.

I feel privileged to be alive at this particular time to witness this sequence!

The sequence of numbers which begin four Harshad numbers in a row are shown at the Online Encyclopedia of Integer Sequences here.