A023797 Katadromes: digits in base 16 are in strict descending order.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 32, 33, 48, 49, 50, 64, 65, 66, 67, 80, 81, 82, 83, 84, 96, 97, 98, 99, 100, 101, 112, 113, 114, 115, 116, 117, 118, 128, 129, 130, 131, 132, 133, 134, 135, 144, 145, 146, 147, 148, 149, 150, 151, 152

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• base
• fini
• easy

Comments

There are 65535 terms, with a(65535) = 18364758544493064720 = FEDCBA9876543210_16. - Michael S. Branicky, Feb 05 2024

Links

• Eric Weisstein's World of Mathematics, Digit.
• Eric Weisstein's World of Mathematics, Katadrome.

Programs

Mathematica

Select[Range[0,200],Max[Differences[IntegerDigits[#,16]]]<0&] (* Harvey P. Dale, Oct 23 2022 *)

Python

from itertools import combinations, islice
def agen(): # generator of terms
    yield 0
    for d in range(1, 17):
        yield from sorted(int("".join(c), 16) for c in combinations("FEDCBA9876543210", d) if c[0] != '0')
print(list(islice(agen(), 50))) # Michael S. Branicky, Feb 05 2024