A329876 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.
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, 22, 17, 42, 105, 31, 2, 4, 27, 96, 42, 5, 72, 19, 20, 22, 32, 102, 31, 104, 4, 24, 95, 21, 13, 12, 9, 38, 3, 58, 38, 78, 31, 119, 31, 45, 107, 42, 12, 9, 21, 66, 181
Offset: 1
Links
- Rémy Sigrist, Table of n, a(n) for n = 1..501
Crossrefs
See A053582 for the corresponding concatenations.
Programs
-
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)))
Formula
The first terms, alongside their concatenations, are:
n a(n) A053582(n)
-- ---- -----------
1 1 1
2 1 11
3 2 211
4 4 4211
5 3 34211
6 2 234211
7 4 4234211
8 15 154234211
9 3 3154234211
10 9 93154234211
Comments