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 A100998 #19 Jul 10 2023 10:04:53 %S A100998 0,1,2,3,4,14,18,19,45,51,52,191,379,587,775,905,1349,1735,2913,7507, %T A100998 15709,16452,17487,18108,21603,25890,26724,34837,67467 %N A100998 Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 63 for n > 0. %C A100998 Numbers n such that 90*10^n + 7 is prime. %C A100998 Numbers n such that digit 9 followed by n >= 0 occurrences of digit 0 followed by digit 7 is prime. %C A100998 Numbers corresponding to terms <= 1349 are certified primes. %C A100998 a(30) > 2*10^5. - _Robert Price_, Oct 16 2015 %D A100998 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. %H A100998 Makoto Kamada, <a href="https://stdkmd.net/nrr/9/90007.htm#prime">Prime numbers of the form 900...007</a>. %H A100998 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %F A100998 a(n) = A096774(n) - 1. %e A100998 90007 is prime, hence 3 is a term. %t A100998 Select[Range[0, 200000], PrimeQ[90*10^# + 7] &] (* _Robert Price_, Oct 16 2015 *) %o A100998 (PARI) a=97;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-63) %o A100998 (PARI) for(n=0,1500,if(isprime(90*10^n+7),print1(n,","))) %Y A100998 Cf. A000533, A002275, A096774. %K A100998 nonn,hard,more %O A100998 1,3 %A A100998 _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 %E A100998 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008 %E A100998 a(25)-a(29) from Kamada data by _Ray Chandler_, Apr 28 2015