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 A101729 #16 Jan 17 2019 13:44:06 %S A101729 0,1,6,8,13,23,44,48,72,73,231,337,396,503,1062,2816,5304,16767,27059 %N A101729 Indices of primes in sequence defined by A(0) = 41, A(n) = 10*A(n-1) + 51 for n > 0. %C A101729 Numbers n such that (420*10^n - 51)/9 is prime. %C A101729 Numbers n such that digit 4 followed by n >= 0 occurrences of digit 6 followed by digit 1 is prime. %C A101729 Numbers corresponding to terms <= 503 are certified primes. %C A101729 a(20) > 10^5. - _Robert Price_, May 27 2015 %D A101729 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. %H A101729 Makoto Kamada, <a href="https://stdkmd.net/nrr/4/46661.htm#prime">Prime numbers of the form 466...661</a>. %H A101729 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %F A101729 a(n) = A102994(n) - 1. %e A101729 461 is prime, hence 1 is a term. %t A101729 Select[Range[0, 1000], PrimeQ[(420*10^# - 51)/9] &] (* _Robert Price_, May 27 2015 *) %o A101729 (PARI) a=41;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+51) %o A101729 (PARI) for(n=0,1500,if(isprime((420*10^n-51)/9),print1(n,","))) %Y A101729 Cf. A000533, A002275, A102994. %K A101729 nonn,hard,more %O A101729 1,3 %A A101729 _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004 %E A101729 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 %E A101729 a(18)-a(19) from Kamada data by _Ray Chandler_, Apr 30 2015