login
A308407
Lexicographically earliest sequence of distinct terms such that reading one-by-one the central pair of digit of each term is the same as reading one-by-one the successive pairs of digits of the sequence itself.
1
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 1110, 1100, 1111, 1000, 1112, 1113, 1101, 1001, 1113, 1120
OFFSET
1,1
COMMENTS
All terms of the sequence have an even number of digits. For terms having only an odd number of digits, see cross-references.
EXAMPLE
The central pair of digits of 10 is 10, of course. The central pair of 1000 is 00. After 99, one reads the successive central pairs 11, 10, 11, 00, 11, 11, 10, 00, 11, 12, ... which are precisely the successive pairs of digits of 1110, 1100, 1111, 1000, 1112, etc.
CROSSREFS
Cf. A308406 (the same idea, but with terms having an odd number of digits).
Sequence in context: A171891 A328075 A001637 * A102494 A117884 A133506
KEYWORD
base,nonn
AUTHOR
Eric Angelini, May 25 2019
STATUS
approved