%I #41 Aug 10 2019 02:36:46
%S 0,12,103,1001,10000,14523,106945,1001823,10007363,100023783,
%T 1000020346
%N Smallest missing number in first 10^n digits after the decimal point in the expansion of Pi.
%H Peter TrĂ¼b, <a href="https://pi2e.ch/blog/2017/03/10/pi-digits-download/">22.4 trillion digits of pi</a>
%e a(1) = 0 because 0 is missing in the first 10^1 = 10 digits after the decimal point in the expansion of Pi, that is, .1415926535...
%e Leading zeros do not count. Thus each of the digit-strings "0", "1", "2", ..., "14522" is present in the first 10^6 digits after the decimal point, but "14523" is not, so a(6) = 14523. - _Robert Israel_, Oct 19 2015
%t Do[With[{r = ToString[FromDigits[Rest[RealDigits[Pi, 10, 10^k][[1]]]]]}, Do[If[StringPosition[r, ToString[n]] == {}, Print[n];k = k + 1; Break[]], {n, 0, 10000000}]], {k, 7}]
%o (Python)
%o start = 0
%o for a in range(1,10):
%o ....with open("pi-billion.txt","r") as f:
%o ........g = f.read(10**a)
%o ....while g.find(str(start)) != -1:
%o ........start += 1
%o ....print(a,start)
%o # http://stuff.mit.edu/afs/sipb/contrib/pi/pi-billion.txt
%o # _David Consiglio, Jr._, Oct 25 2014
%Y Cf. A000796, A228989, A228990, A260627, A260628.
%K nonn,base,more
%O 1,2
%A _Shyam Sunder Gupta_, Sep 10 2013
%E More terms from _David Consiglio, Jr._, Oct 25 2015
%E a(10)-a(11) from _Giovanni Resta_, Aug 10 2019