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A275542 The digits of the integers with the nonprimes removed.

%I A275542 #35 Dec 28 2019 14:57:56
%S A275542 2,3,5,7,2,3,5,7,2,2,2,2,2,3,2,2,5,2,2,7,2,2,3,3,3,2,3,3,3,3,5,3,3,7,
%T A275542 3,3,2,3,5,7,5,5,5,2,5,3,5,5,5,5,5,7,5,5,2,3,5,7,7,7,7,2,7,3,7,7,5,7,
%U A275542 7,7,7,7,2,3,5,7,2,3,5,7
%N A275542 The digits of the integers with the nonprimes removed.
%C A275542 Write the digits of the positive integers one by one: 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 0, 1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9, 2, 0, 2, 1, etc. (this is A007376). Then from that sequence, remove the nonprimes, leaving a sequence that consists entirely of 2s, 3s, 5s and 7s.
%H A275542 Metin Sariyar, <a href="/A275542/b275542.txt">Table of n, a(n) for n = 1..32000</a> (terms 1..2401 from Robert Price)
%e A275542 From the single-digit numbers, we obviously get the first four terms of this sequence: 2, 3, 5, 7.
%e A275542 10 is composite and neither of its digits is a single-digit prime, so it contributes nothing to this sequence.
%e A275542 11 is prime but its digits consist of two 1s, so like 10 it also contributes nothing to the sequence.
%e A275542 12 is composite, but its least significant digit is 2, which is a prime, and thus 12 contributes a 2 to the sequence.
%t A275542 Flatten[Table[Select[IntegerDigits[n], PrimeQ], {n, 100}]] (* _Alonso del Arte_, Aug 01 2016 *)
%Y A275542 Cf. A007376, A033307.
%K A275542 nonn,base
%O A275542 1,1
%A A275542 _Dave Durgin_, Aug 01 2016