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 A111175 #10 Feb 17 2017 14:55:36 %S A111175 1,2,5,6,7,8,9,11,14,18,19,20,21,22,23,25,27,33,34,35,39,40,41,43,44, %T A111175 46,49,51,54,58,60,61,62,65,67,71,72,74,75,76,77,78,79,84,85,89,91,93, %U A111175 95,99,100,102,104,106,109,110,111,112,113,117,118,119,121,123,131,134,135 %N A111175 Numbers n such that 30*n + 1 is prime. %C A111175 Encoded primes with LSD 1 and (SOD-1)/3 integer, (LSD, least significant digit; SOD, sum of digits). Divide any such number by 30, if the whole number portion of the quotient is in the sequence, the number is prime. Example: 2671, with LSD 1 and (SOD-1)/3 = 2 (integer); Then 2671/30 = 89.033, or 89, which is in the sequence, and thus 2671 is prime. - _Ki Punches_, Mar 18 2009 %F A111175 a(n) = (A132230(n) - 1)/30 = Floor[A132230(n)/30]. - Chandler %e A111175 If n=99 then 30*n + 1 = 2971 (prime). %o A111175 (PARI) is(n)=isprime(30*n+1) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A111175 Cf. A158573, A158614, A158648, A158746, A158791, A158806, A158850. %K A111175 nonn %O A111175 1,2 %A A111175 _Parthasarathy Nambi_, Oct 21 2005 %E A111175 Extended by _Ray Chandler_, Apr 07 2009