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 A101849 #20 Jan 17 2019 13:44:06 %S A101849 0,1,13,19,29,43,65,259,871,8845,26743,57505,98471,106891 %N A101849 Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) + 27 for n > 0. %C A101849 Numbers n such that (360*10^n - 27)/9 is prime. %C A101849 Numbers n such that digit 3 followed by n >= 0 occurrences of digit 9 followed by digit 7 is prime. %C A101849 Numbers corresponding to terms <= 871 are certified primes. %C A101849 a(14) > 10^5. - _Robert Price_, Mar 17 2015. %C A101849 a(15) > 2*10^5. - _Robert Price_, Oct 02 2015 %D A101849 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. %H A101849 Makoto Kamada, <a href="https://stdkmd.net/nrr/3/39997.htm#prime">Prime numbers of the form 399...997</a>. %H A101849 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %F A101849 a(n) = A101398(n) - 1. %e A101849 397 is prime, hence 1 is a term. %t A101849 Select[Range[0, 1000], PrimeQ[(360*10^# - 27)/9] &] (* _Robert Price_, Mar 17 2015 *) %o A101849 (PARI) a=37;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+27) %o A101849 (PARI) for(n=0,1500,if(isprime((360*10^n-27)/9),print1(n,","))) %Y A101849 Cf. A000533, A002275, A101155, A169830, A101398. %K A101849 nonn,hard,more %O A101849 1,3 %A A101849 _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004 %E A101849 8845 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 %E A101849 a(11)-a(13) derived from A101398 by _Robert Price_, Mar 17 2015 %E A101849 a(14) from _Robert Price_, Oct 02 2015