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A165449 Write the prime numbers in a string: 2357111317192329... (cf. A033308). The sequence gives the first position in the string for natural numbers.

%I A165449 #22 May 01 2021 11:56:59
%S A165449 5,1,2,21,3,31,4,41,12,47,5,62,7,22,77,32,9,95,11,589,110,113,1,128,
%T A165449 131,137,63,149,15,158,8,14,123,24,2,188,19,42,72,206,21,215,23,227,
%U A165449 233,236,25,248,75,257,78,263,27,269,275,278,3,290,29,299,31,829
%N A165449 Write the prime numbers in a string: 2357111317192329... (cf. A033308). The sequence gives the first position in the string for natural numbers.
%C A165449 Same as A229190 but omitting the a(0) term.
%C A165449 Defined for all a by the normality of the Copeland-Erdős constant. - _Aaron Weiner_, Sep 19 2013
%H A165449 Nathaniel Johnston, <a href="/A165449/b165449.txt">Table of n, a(n) for n = 1..5000</a>
%e A165449 The first occurrence of "111" in the string is 5, so a(111)=5.
%p A165449 with(StringTools): s:="": for n from 1 to 300 do s:=cat(s,convert(ithprime(n),string)): od: seq(Search(convert(n,string),s),n=1..62); # _Nathaniel Johnston_, May 26 2011
%t A165449 With[{prd=Flatten[IntegerDigits/@Prime[Range[1000]]],nn=10},Flatten[ Table[ SequencePosition[ prd,IntegerDigits[ n],1],{n,70}],1]][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 12 2019 *)
%o A165449 (Python)
%o A165449 from sympy import primerange
%o A165449 from itertools import count, takewhile
%o A165449 def afind(plimit):
%o A165449   s = "".join(str(p) for p in primerange(1, plimit+1))
%o A165449   return [1+s.find(str(n)) for n in takewhile(lambda i: str(i) in s, count(1))]
%o A165449 print(afind(10**4)) # _Michael S. Branicky_, May 01 2021
%Y A165449 Cf. A229190 (same sequence but including the a(0) term).
%Y A165449 Cf. A031297.
%K A165449 easy,base,nonn
%O A165449 1,1
%A A165449 _Rémy Sigrist_, Sep 20 2009