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 A265383 #96 May 03 2024 23:22:54 %S A265383 1,6,9,154,253,1114,1390,2618,5611,12871,15286,108609,132574,164369, %T A265383 188484 %N A265383 Numbers k such that 10^k * (10^k - 1) - 1 is prime. %C A265383 The primes arising from this construction (e.g., 999998999999) are among the primes counted in A266148. In particular, it follows that A266148(a(n)) > 0. - _David A. Corneth_, May 19 2016 %C A265383 a(16) > 188484. - _Ben Meekins_, Sep 08 2018 %H A265383 Brady Haran and Simon Pampena, <a href="https://www.youtube.com/watch?v=HPfAnX5blO0">Glitch Primes and Cyclops Numbers</a>, Numberphile video (2015). %H A265383 M. Kamada, <a href="https://stdkmd.net/nrr/prime/">Near-repdigit-related prime numbers</a> %e A265383 6 is in the sequence because 10^12 - 10^6 - 1 = 999998999999 is prime. %t A265383 Select[Range[15000], PrimeQ[10^# (10^# - 1) - 1] &] (* _Vincenzo Librandi_, Dec 08 2015 *) %o A265383 (PARI) for(n=1,9999,if(ispseudoprime(10^n*(10^n-1)-1),print1(n", "))) %o A265383 (Magma) [n: n in [0..200] | IsPrime(10^n*(10^n-1)-1)]; // _Vincenzo Librandi_, Dec 08 2015 %Y A265383 Cf. similar sequences listed in A265481. %Y A265383 A098845: Similar sequence in base 2. %Y A265383 A183187: Numbers k such that 10^(2k+1)-10^k-1 is prime, palindromic. %Y A265383 A266148: Number of n-digit primes in which n-1 of the digits are 9's. %K A265383 nonn,more %O A265383 1,2 %A A265383 _Serge Batalov_, Dec 07 2015 %E A265383 a(11) from Kazuyoshi Asao, Feb 11 2002 %E A265383 a(12) from _Serge Batalov_, Dec 25 2015 %E A265383 a(13) from _Ben Meekins_, Feb 16 2016 %E A265383 a(14) from _Ben Meekins_, Dec 17 2016 %E A265383 a(15) from _Ben Meekins_, Sep 08 2018