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

1,3

Comments

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

Links

Rémy Sigrist, Table of n, a(n) for n = 1..501

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

Prog

(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)))

Crossrefs

See A053582 for the corresponding concatenations.

Sequence in context: A345928 A060806 A320044 * A128868 A341073 A095986

Adjacent sequences: A329873 A329874 A329875 * A329877 A329878 A329879

Keyword

nonn,base

Author

Rémy Sigrist, Nov 23 2019

Status

approved