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 A161786 #9 Feb 21 2019 23:14:55
%S A161786 10111,11113,11117,11119,11131,11161,11171,11311,11411,16111,22229,
%T A161786 23333,31333,33331,33343,33353,33533,38333,44449,47777,49999,59999,
%U A161786 67777,71777,76777,77377,77477,77747,77773,77797,77977,79777,79999,88883,94999,97777
%N A161786 Primes with at least one digit appearing exactly four times in the decimal expansion.
%C A161786 The sequence is probably infinite.
%H A161786 Harvey P. Dale, <a href="/A161786/b161786.txt">Table of n, a(n) for n = 1..2000</a>
%e A161786 101117 has exactly four 1s.
%p A161786 isdgctm := proc(n,d) local dgs,a,i ; dgs := convert(n,base,10) ; a := [seq(0,j=0..9)] ;
%p A161786 for i in dgs do a := subsop(i+1=op(i+1,a)+1,a) ; od: if convert(a,set) intersect {d} <> {} then true; else false; fi; end:
%p A161786 for n from 1 to 10000 do p := ithprime(n) ; if isdgctm(p,4) then printf("%d,",p) ; fi; od: # _R. J. Mathar_, Jun 21 2009
%t A161786 Select[Prime[Range[186,10000]],MemberQ[DigitCount[#],4]&] (* _Harvey P. Dale_, Apr 12 2015 *)
%K A161786 nonn,base
%O A161786 1,1
%A A161786 _Ki Punches_, Jun 19 2009
%E A161786 Edited and corrected by _R. J. Mathar_, Jun 21 2009