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

Author

Amarnath Murthy, Mar 13 2002

Keywords

• nonn
• base

Comments

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

Examples

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

Links

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

Crossrefs

Cf. A068861.

Programs

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

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

Extensions

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