A068860 a(1) = 1; a(n+1) is the smallest number > a(n) which differs from it at every digit.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 21, 30, 41, 50, 61, 70, 81, 90, 101, 210, 301, 410, 501, 610, 701, 810, 901, 1010, 2101, 3010, 4101, 5010, 6101, 7010, 8101, 9010, 10101, 21010, 30101, 41010, 50101, 61010, 70101, 81010, 90101, 101010, 210101, 301010, 410101, 501010

Offset

1,2

Comments

a(9001) has 1001 digits. - Michael S. Branicky, Mar 19 2024

Links

Michael S. Branicky, Table of n, a(n) for n = 1..9000

Formula

a(n) = fabab... where f = ((n-1) mod 9) + 1 and ab = 01 if f is odd else 10 and has floor((n-1)/9)+1 digits. - Michael S. Branicky, Mar 19 2024

Example

After 90 the next member is 101 which differs at each digit position.

Prog

(Python)
def a(n):
    q, r = divmod(n-1, 9)
    d, f = q+1, r+1
    return int((str(f) + "0"*(f%2) + "10"*(d//2))[:d])
print([a(n) for n in range(1, 51)]) # Michael S. Branicky, Mar 19 2024

Crossrefs

Cf. A068861.

Sequence in context: A256079 A216556 A331975 * A158699 A247107 A061511

Adjacent sequences: A068857 A068858 A068859 * A068861 A068862 A068863

Keyword

nonn,base

Author

Amarnath Murthy, Mar 13 2002

Extensions

a(48) and beyond from Michael S. Branicky, Mar 19 2024

Status

approved