A324280 Lexicographically earliest sequence of different terms starting with a(1) = 2 such that the n-th digit of the sequence, placed in front of a(n) and then concatenated, produces a composite number.

2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 1, 15, 13, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 28, 29, 27, 31, 32, 34, 35, 36, 33, 37, 38, 42, 39, 43, 44, 45, 41, 46, 48, 47, 49, 51, 52, 54, 53, 55, 56, 57, 58, 61, 62, 63, 64, 65, 59, 66, 67, 68, 72, 69, 73, 71, 74, 75, 76, 77, 78, 81, 82, 83, 79, 84, 85, 86, 88, 89, 87, 91, 92, 94, 95, 96

Offset

1,1

Comments

No digit 0 is admitted in a(n) in order to avoid leading zeroes after the concatenation.

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10009

Example

The 1st digit of the sequence (2) concatenated to the 1st term = 22 (composite);
The 2nd digit of the sequence (3) concatenated to the 2nd term = 33 (composite);
The 3rd digit of the sequence (4) concatenated to the 3rd term = 44 (composite);
The 4th digit of the sequence (5) concatenated to the 4th term = 55 (composite);
The 5th digit of the sequence (6) concatenated to the 5th term = 66 (composite);
The 6th digit of the sequence (7) concatenated to the 6th term = 77 (composite);
The 7th digit of the sequence (8) concatenated to the 7th term = 88 (composite);
The 8th digit of the sequence (9) concatenated to the 8th term = 99 (composite);
The 9th digit of the sequence (1) concatenated to the 9th term = 111 (composite);
The 10th digit of the sequence (1) concatenated to the 10th term = 112 (composite);
etc.

Crossrefs

Cf. A306311, A306321, A324279, A324281 and A324282 where the same idea is used.

Sequence in context: A254785 A126969 A127274 * A324281 A129946 A099649

Adjacent sequences: A324277 A324278 A324279 * A324281 A324282 A324283

Keyword

base,nonn

Author

Eric Angelini and Jean-Marc Falcoz, Feb 20 2019

Status

approved