A257793 - OEIS

%I #7 Jan 02 2023 12:30:51

%S 1,3,2,5,6,7,10,9,8,13,12,11,16,15,14,21,18,19,22,23,20,25,24,29,28,

%T 27,26,31,30,37,36,33,34,39,38,35,42,41,40,43,48,47,46,45,44,51,50,49,

%U 52,53,56,55,54,59,58,57,70,69,68,61,66,63,64,67,71,73,72

%N Lexicographically earliest injective sequence such that a(n)+a(a(n)) is prime

%C "Lexicographically earliest injective sequence" means that a(n+1) is the least positive integer not occurring earlier with the given property.

%H Lars Blomberg, <a href="/A257793/b257793.txt">Table of n, a(n) for n = 1..10000</a>

%H E. Angelini, <a href="http://list.seqfan.eu/oldermail/seqfan/2015-April/014684.html">a(n)+a(a(n)) is prime</a>, Seqfan (Apr 11 2015)

%e a(1)=1, a(a(1))=1, 1+1=2 which is prime.

%e a(7)=10, a(a(7))=a(10)=13, 10+13=23 which is prime.

%K nonn

%O 1,2

%A _Eric Angelini_ and _Lars Blomberg_, May 11 2015