This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A375777 #10 Oct 02 2024 14:38:52 %S A375777 8,9,12,16,18,24,25,27,28,32,36,40,45,48,49,54,56,60,63,64,75,76,84, %T A375777 90,96,98,100,108,112,120,121,124,126,136,144,148,152,153,160,171,175, %U A375777 180,184,189,196,198,204,207,208,220,228,232,243,250,261,264,270,276 %N A375777 Numbers k such that k - rad(k) - 1 is prime, where rad(k) is A007947(k). %e A375777 12 is a term, because 12 - rad(12) - 1 = 12 - (2 * 3) - 1 = 12 - 6 - 1 = 5 is prime. %t A375777 Select[Range[300], PrimeQ[# - Times @@ FactorInteger[#][[;; , 1]] - 1] &] (* _Amiram Eldar_, Aug 27 2024 *) %o A375777 (PARI) isok(k) = isprime(k - (vecprod(factor(k)[, 1])) - 1); %Y A375777 Cf. A007947, A097379, A359213, A374593. %K A375777 nonn %O A375777 1,1 %A A375777 _Arsen Vardanyan_, Aug 27 2024