# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a280019 Showing 1-1 of 1 %I A280019 #16 Jun 09 2024 22:16:23 %S A280019 1,2,3,5,10,23,29,56,68,199,364,436,478,1178,1187,1869,4733,11816, %T A280019 11867,17383,27987,42005,51889,111770,113176,168541 %N A280019 Numbers k such that (94*10^k + 11)/3 is prime. %C A280019 For k > 1, numbers k such that the digits 31 followed by k-1 occurrences of the digit 3 followed by the digit 7 is prime (see Example section). %C A280019 a(27) > 2*10^5. %H A280019 Makoto Kamada, Factorization of near-repdigit-related numbers. %H A280019 Makoto Kamada, Search for 313w7. %e A280019 3 is in this sequence because (94*10^3 + 11)/3 = 31337 is prime. %e A280019 Initial terms and associated primes: %e A280019 a(1) = 1, 317; %e A280019 a(2) = 2, 3137; %e A280019 a(3) = 3, 31337; %e A280019 a(4) = 5, 3133337; %e A280019 a(5) = 10, 313333333337; etc. %t A280019 Select[Range[0, 100000], PrimeQ[(94*10^# + 11)/3] &] %Y A280019 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A280019 nonn,more,hard %O A280019 1,2 %A A280019 _Robert Price_, Feb 21 2017 %E A280019 a(24)-a(26) from _Robert Price_, Apr 03 2020 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE