A329876 - OEIS

%I #10 Nov 23 2019 13:59:12

%S 1,1,2,4,3,2,4,15,3,9,20,4,3,11,31,6,24,23,82,11,21,3,22,20,63,19,56,

%T 22,17,42,105,31,2,4,27,96,42,5,72,19,20,22,32,102,31,104,4,24,95,21,

%U 13,12,9,38,3,58,38,78,31,119,31,45,107,42,12,9,21,66,181

%N Lexicographically earliest sequence of positive integers such that for n > 1, the concatenation of a(n), a(n-1), ..., a(1), in decimal, is a prime number.

%C For any n > 0, the concatenation of a(n+1) and A053582(n) gives A053582(n+1).

%H Rémy Sigrist, <a href="/A329876/b329876.txt">Table of n, a(n) for n = 1..501</a>

%F The first terms, alongside their concatenations, are:

%F   n   a(n)  A053582(n)

%F   --  ----  -----------

%F    1     1            1

%F    2     1           11

%F    3     2          211

%F    4     4         4211

%F    5     3        34211

%F    6     2       234211

%F    7     4      4234211

%F    8    15    154234211

%F    9     3   3154234211

%F   10     9  93154234211

%o (PARI) print1 (v=1); for (n=2, 69, s=(b=10)^#digits(v,b); for (k=1, oo, if (isprime(v+=s), print1 (", "k); break)))

%Y See A053582 for the corresponding concatenations.

%K nonn,base

%O 1,3

%A _Rémy Sigrist_, Nov 23 2019