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 A108251 #23 Jul 06 2019 16:44:21 %S A108251 797,911,1287,2127,2217,2247,2303,2457,2841,3221,3407,3531,3921,4353, %T A108251 4361,4403,5097,5459,5867,6173,6261,6531,6741,6939,7133,7271,7311, %U A108251 7707,7797,8651,8841,8951,9347,9401,9599,9669,9729,10001,10773,10937,11663 %N A108251 Numbers n such that googol - n is prime. %C A108251 This sequence is finite with between 4.361969*10^97 and 4.361998*10^97 terms. Under the Riemann Hypothesis, it has 4.361971987140703159099509113229164611538757211...*10^97 terms. - _Charles R Greathouse IV_, Nov 23 2009 %C A108251 10^100-a(148) and 10^100-a(149) are the last twin primes less than 10^100. - _T. D. Noe_, Nov 03 2008 %H A108251 T. D. Noe, <a href="/A108251/b108251.txt">Table of n, a(n) for n = 1..1000</a> %H A108251 For each of the 1000 terms in the table, 10^100 - a(n) was verified by the <a href="http://magma.maths.usyd.edu.au/calc/">Magma Calculator</a> as prime. - _Jon E. Schoenfield_, Aug 24 2009 %e A108251 A googol = 10^100. 10^100 - 797 is prime, so 797 is in the sequence. %t A108251 Rest[10^100-#&/@NestList[NextPrime[#,-1]&,10^100,50]] (* _Harvey P. Dale_, Jan 23 2017 *) %o A108251 (PARI) forstep(x=1,n,2,if(isprime(10^100-x),print1(x","))) %Y A108251 Cf. A049014, A133282. %K A108251 easy,nonn,fini %O A108251 1,1 %A A108251 _Cino Hilliard_, Jun 17 2005 %E A108251 Edited by _Charles R Greathouse IV_, Nov 23 2009