A277998 - OEIS

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A277998

Lexicographically first sequence (with no duplicates) where the last digit of a(n) added to the first digit of a(n+1) equals 10.

1, 9, 11, 91, 92, 8, 2, 81, 93, 7, 3, 71, 94, 6, 4, 61, 95, 5, 51, 96, 41, 97, 31, 98, 21, 99, 12, 82, 83, 72, 84, 62, 85, 52, 86, 42, 87, 32, 88, 22, 89, 13, 73, 74, 63, 75, 53, 76, 43, 77, 33, 78, 23, 79, 14, 64, 65, 54, 66, 44, 67, 34, 68, 24, 69, 15, 55, 56, 45, 57, 35, 58, 25, 59, 16, 46, 47, 36, 48, 26, 49, 17, 37, 38, 27, 39, 18, 28, 29, 19, 101, 901, 902, 801, 903, 701, 904, 601, 905, 501, 906, 401, 907, 301, 908, 201

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

OFFSET

1,2

COMMENTS

The sequence starts with a(1) = 1 and was always extended with the smallest integer not yet present that does not lead to a contradiction.

LINKS

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001

EXAMPLE

The sequence begins with 1, 9, 11, 91, 92, 8, 2, 81, 93, 71... The two digits that border the first comma are 1 and 9 that sum up to 10 as required; the 2nd comma is bordered by 9 and 1; the 3rd one by 1 and 9 again; the 4th one by 1 and 9 too; the 5th one by 2 and 8; the 6th one by 8 and 2; the 7th one by 2 and 8 again; the 8th one by 1 and 9; the 9th one by 3 and 7, etc.

CROSSREFS

Sequence in context: A108687 A038301 A359925 * A289288 A137016 A053886

Adjacent sequences: A277995 A277996 A277997 * A277999 A278000 A278001

KEYWORD

nonn,base

AUTHOR

Eric Angelini and Jean-Marc Falcoz, Nov 08 2016

STATUS

approved