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 A186206 #13 Sep 15 2017 23:15:43
%S A186206 5,53,577,3359,64901,939923,2402431,72156649,215664901,7215664901,
%T A186206 24310421593,721566490153,2359880576723,42159335939923,
%U A186206 359399235988057,6749514631447249,98805767234884867,402431042159335939
%N A186206 The first n-digit prime in the decimal expansion of gamma, the Euler-Mascheroni constant.
%C A186206 Euler-Mascheroni Gamma = 0.577215664901532860606512090082402431042...
%e A186206 Positions in A001620: 1, 13, 1, 43, 8, 46, 30, 3, 4, 3, 33, 3, 50, 38, 44, 96, 53, 31, 40, 64, ...
%p A186206 Digits := 10000: p0 := evalf(gamma)*10:for d from 1 to 20 do: id:=0:for i from
%p A186206 0 to 50000 while(id=0) do :q0:=trunc(p0*10^(i+d-1)): x:= irem(q0,10^d): if type(x,prime)=true
%p A186206 and length(x)=d then printf(`%d, `,x):id:=1: else fi:od:od:~
%t A186206 With[{eg=RealDigits[EulerGamma,10,250][[1]]},Table[First[Select[ FromDigits/@Partition[eg,n,1],PrimeQ[#]&&IntegerLength[#]==n&]], {n,20}]] (* _Harvey P. Dale_, Sep 29 2011 *)
%Y A186206 Cf. A001620.
%K A186206 nonn,base
%O A186206 1,1
%A A186206 _Michel Lagneau_, Feb 15 2011