Saturday, 12 October 2024

Record Runs Involving Home Primes

I just happened to notice that there is a run of six consective numbers from 27597 to 27602 inclusive that are only one step removed from their home primes. The only longer run up to one million that occurs is a run of eight numbers from 45162 to 45169.

Here is a permalink for finding these runs. Currently I'm 27586 days old and so the coming record run is not far off. Here are the factorisations for the numbers and the home primes associated with them.

  • 27597=3×919939199

  • 27598=2×13799213799

  • 27599=11×13×1931113193

  • 27600=24×3×52×23222235523

  • 27601=7×394373943

  • 27602=2×37×373237373
The run of eight numbers is listed below together with factorisations and home primes:

  • 45162=2×32×13×19323313193

  • 45163=19×2377192377

  • 45164=22×7×16132271613

  • 45165=3×5×3011353011

  • 45166=2×11×20532112053

  • 45167=312×47313147

  • 45168=24×3×94122223941

  • 45169=17×2657172657
All concatenations are applied to the prime factors in order from lowest to highest. Of course, runs formed by numbers that are concatenations of prime factors from highest to lowest are impossible because every second number is even with a smallest factor of 2. Every second concatenated number will thus be even as well.

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