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 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. 4
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified August 8 19:29 EDT 2020. Contains 336298 sequences. (Running on oeis4.)