A004287 Least positive multiple of n written in base 7 using only 0 and 1.

1, 11, 111, 11, 101, 111111, 10, 11, 1011, 101, 10011, 111111, 1011, 110, 11001, 1111, 100111, 1101111, 111, 1111, 1110, 11101, 101011, 111111, 101, 111001, 1011, 110, 1111111, 1011111, 100111, 11011, 10011, 100111, 1010, 1101111

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

With[{cl=Rest[{FromDigits[#, 7], FromDigits[#]}&/@Tuples[{0, 1}, 7]]}, Table[ SelectFirst[ cl, Mod[#[[1]], n]==0&], {n, 40}]][[;; , 2]] (* Harvey P. Dale, Jan 31 2024 *)

Prog

(Python)
def A004287(n):
    if n > 0:
        for i in range(1, 2**n):
            s = bin(i)[2:]
            if not int(s, 7) % n:
                return int(s)
    return 0 # Chai Wah Wu, Dec 30 2014

Crossrefs

Cf. A244958 (written in base 10).

Sequence in context: A055016 A259372 A348871 * A061493 A093788 A327992

Adjacent sequences: A004284 A004285 A004286 * A004288 A004289 A004290

Keyword

nonn,base

Author

David W. Wilson

Extensions

Removed initial 0 since (1) it did not match the definition, and (2) there are many similar sequences with the same author which also say "positive". Also changed offset. - N. J. A. Sloane, Jan 31 2024

Previous b-file replaced by Harvey P. Dale, Jan 31 2024

Status

approved