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

1,3

Comments

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

Links

Table of n, a(n) for n=1..61.

Eric Weisstein's World of Mathematics, Digit.

Eric Weisstein's World of Mathematics, Katadrome.

Mathematica

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

Prog

(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

Crossrefs

Sequence in context: A023770 A371864 A357979 * A032951 A288139 A194897

Adjacent sequences: A023794 A023795 A023796 * A023798 A023799 A023800

Keyword

nonn,base,fini,easy

Author

Olivier Gérard

Status

approved