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 A273002 #13 May 02 2024 04:24:32 %S A273002 0,2,3,4,18,21,36,58,68,78,84,94,150,178,190,591,686,812,840,2308, %T A273002 2530,2884,4311,6134,7695,8004,8109,9777,15570,17505 %N A273002 Numbers k such that 16*10^k + 1 is prime. %C A273002 For k > 1, numbers k such that the digits 16 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section). %C A273002 a(31) > 10^5. %H A273002 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %H A273002 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 160w1</a>. %e A273002 4 is in this sequence because 16*10^4+1 = 160001 is prime. %e A273002 Initial terms and associated primes: %e A273002 a(1) = 0, 17; %e A273002 a(2) = 2, 1601; %e A273002 a(3) = 3, 16001; %e A273002 a(4) = 4, 160001; %e A273002 a(5) = 18, 16000000000000000001. etc. %t A273002 Select[Range[0, 100000], PrimeQ[16*10^#+1] &] %o A273002 (PARI) is(n)=ispseudoprime(16*10^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A273002 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. %K A273002 nonn,more %O A273002 1,2 %A A273002 _Robert Price_, May 12 2016