cp's OEIS Frontend

A303782 Lexicographically earliest sequence of distinct terms such that what emerges from the mask is prime (see the Comment section for the mask explanation).

%I A303782 #12 Dec 01 2019 23:14:29
%S A303782 1,12,2,13,3,15,4,17,5,22,6,23,7,25,8,27,9,32,102,10,103,11,105,14,
%T A303782 107,16,112,18,113,19,115,20,117,21,122,24,123,26,125,28,127,29,132,
%U A303782 30,133,31,135,33,137,34,142,35,143,36,145,37,147,38,152,39,153,40,155,41,157,42,162,43,163,44,165,45,167,46,172,47
%N A303782 Lexicographically earliest sequence of distinct terms such that what emerges from the mask is prime (see the Comment section for the mask explanation).
%C A303782 For any pair of contiguous terms, one of the terms uses fewer digits than the other. This term is called the mask. Put the mask on the other term, starting from the left. What is not covered by the mask forms a prime number.
%C A303782 The sequence starts with a(1) = 1 and is always extended with the smallest integer not yet present that doesn't lead to a contradiction.
%C A303782 This sequence is a permutation of the integers > 0, as all integers will appear at some point, either as mask or masked.
%H A303782 Jean-Marc Falcoz, <a href="/A303782/b303782.txt">Table of n, a(n) for n = 1..10001</a>
%e A303782 In the pair (1,12), 1 is the mask; 2 emerges and is prime;
%e A303782 In the pair (12,2), 2 is the mask; 2 emerges and is prime;
%e A303782 In the pair (2,13), 2 is the mask; 3 emerges and is prime;
%e A303782 In the pair (13,3), 3 is the mask; 3 emerges and is prime;
%e A303782 ...
%e A303782 In the pair (11525,2018), 2018 is the mask; 5 emerges and is prime;
%e A303782 etc.
%Y A303782 Cf. A303783 (same idea with squares), A303784 (with even numbers), A303785 (with odd numbers), A303786 (rebuilds term by term the sequence itself).
%K A303782 nonn,base
%O A303782 1,2
%A A303782 _Eric Angelini_ and _Jean-Marc Falcoz_, Apr 30 2018