2020 gone for good. Welcome 2021! - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: General Forum (/forum-4.html) +--- Thread: 2020 gone for good. Welcome 2021! (/thread-16103.html) 2020 gone for good. Welcome 2021! - Gerson W. Barbosa - 01-01-2021 03:17 AM RE: 2020 gone for good. Welcome 2021! - Dave Britten - 01-01-2021 04:39 AM 20201231 and 20210101 are both prime numbers. Maybe it's a good sign... RE: 2020 gone for good. Welcome 2021! - rprosperi - 01-01-2021 04:57 AM Awesome job Gerson, I LOVE seeing the New Year greeted by an HP-75C!! And something about the fact that both of those number are Prime, and even more so that Dave thought to check their primeness, bodes well for a better year. Happy New Year everybody! RE: 2020 gone for good. Welcome 2021! - Gamo - 01-01-2021 05:40 AM Happy New Year 2021 [attachment=8975] Gamo RE: 2020 gone for good. Welcome 2021! - Massimo Gnerucci - 01-01-2021 08:49 AM Something terribly wrong must've happened here! [attachment=8976] Happy (new) year! RE: 2020 gone for good. Welcome 2021! - DA74254 - 01-01-2021 09:49 AM Happy New Year. Welcome 2021. RE: 2020 gone for good. Welcome 2021! - Sylvain Cote - 01-01-2021 12:08 PM Happy New Year! RE: 2020 gone for good. Welcome 2021! - MNH - 01-01-2021 05:12 PM Happy New Year 2021! [attachment=8977] RE: 2020 gone for good. Welcome 2021! - Valentin Albillo - 01-01-2021 06:38 PM (01-01-2021 04:39 AM)Dave Britten Wrote:  20201231 and 20210101 are both prime numbers. Maybe it's a good sign... Indeed they are. As for 2021, it's composite and readily factorized a la Fermat, like this:             2021 = 2025 - 4 = 452 - 22 = (45 - 2) * (45 + 2) = 43 * 47. Happy New Year 2021 ! V. RE: 2020 gone for good. Welcome 2021! - Nihotte(lma) - 01-01-2021 07:04 PM Happy New Year 2021 ! Laurent RE: 2020 gone for good. Welcome 2021! - twoweims - 01-02-2021 01:28 AM (01-01-2021 04:39 AM)Dave Britten Wrote:  20201231 and 20210101 are both prime numbers. Maybe it's a good sign... This will not be true next year... I wonder how often this happens and when will be the next time? RE: 2020 gone for good. Welcome 2021! - Jlouis - 01-02-2021 01:31 AM Happy NEW YEAR !!! Stay safe, protect the ones you love and the ones you don't love too! Love all! P.S.: I have a feeling that I made a mistake in the picture above, but I cannot find which.....never mind.... RE: 2020 gone for good. Welcome 2021! - twoweims - 01-02-2021 02:46 AM (01-02-2021 01:28 AM)twoweims Wrote:   (01-01-2021 04:39 AM)Dave Britten Wrote:  20201231 and 20210101 are both prime numbers. Maybe it's a good sign... This will not be true next year... I wonder how often this happens and when will be the next time? My HP-71 says it happens at the end of these years: Code: ```  4                    103                  160                  190                  211                  271                  304                  346                  367                  376                  451                  475                  502                  550                  586                  649                  736                  799                  817                  874                  937                  1000                 1018                 1051                 1084                 1126                 1153                 1159                 1165                 1186                 1198                 1237                 1468                 1513                 1555                 1600                 1621                 1747                 1810                 1828                 1891                 1930                 1972                 1978                 1987                 2020                 2029```