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 A219998 #6 Dec 08 2012 02:18:28 %S A219998 114,134,135,168,219,249,315,324,348,375,419,431,477,485,513,525,537, %T A219998 546,561,576,597,641,651,675,693,709,714,727,738,777,798,834,840,848, %U A219998 849,891,908,936,945,957,999,1002,1005,1038,1041,1081,1082,1092,1134,1176 %N A219998 Prime-free decades such that the previous decade is also prime-free. %C A219998 Numbers n such that 10n-9, 10n-7, 10n-3, 10n-1, 10n+1, 10n+3, 10n+7, and 10n+9 are composite. %H A219998 V. Raman, <a href="/A219998/b219998.txt">Table of n, a(n) for n = 1..10000</a> %F A219998 a(n) ~ n. %F A219998 a(n) = A216288(n) + 1. %o A219998 (PARI) for(i=2, 1200, if(isprime(10*i-9)==0&&isprime(10*i-7)==0&&isprime(10*i-3)==0&&isprime(10*i-1)==0&&isprime(10*i+1)==0&&isprime(10*i+3)==0&&isprime(10*i+7)==0&&isprime(10*i+9)==0, print1(i", "))) %Y A219998 Cf. A190639, A032352. %Y A219998 Cf. A216288 (lower decade). %K A219998 nonn,base %O A219998 1,1 %A A219998 _V. Raman_, Dec 07 2012