A108401 A Langford-like sequence.

5, 6, 7, 8, 9, 15, 16, 17, 18, 29, 42, 63, 74, 83, 161, 273, 286, 300, 400, 684, 900, 1315, 1319, 1513, 1813, 1913, 2582, 3005, 3006, 3007, 3161, 3187, 3600, 3928, 4200, 5429, 6251, 7126, 12147, 16143, 19134, 20024, 39003, 40000, 40003, 40031, 41001, 41009

Offset

5,1

Comments

Construction rules: 1) a(n) < a(n+1) 2) if you pick any digit "d" of the sequence, the closest identical one is at exactly "d" digits from it (jumping to the right or to the left).

Links

Table of n, a(n) for n=5..52.

Example

Pick the leftmost "5" and jump 5 digits (to the right): you'll land on another "5".
Pick the third "6" (visible in 63) and jump 6 digits (to the right): you'll land on another "6" (161). [Jumping again 6 digits from there to the right would send you on another "6" (286), which is allowed].
Pick the first "0" (300) and jump 0 digits (to the right): you'll move to the next digit, which is a "0".
Note that the rule (2) forbids integers like "323" because if you pick one of those 3's the *closest* copy is at a "1" jump -- and not at a "3" jump, which is mandatory.

Crossrefs

Sequence in context: A047577 A293481 A174138 * A125298 A037362 A102717

Adjacent sequences: A108398 A108399 A108400 * A108402 A108403 A108404

Keyword

base,easy,nonn

Author

Eric Angelini, Jul 03 2005

Status

approved