A357030 a(n) is the number of integers in 0..n having nonincreasing digits.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 14, 15, 15, 15, 15, 15, 15, 15, 15, 16, 17, 18, 19, 19, 19, 19, 19, 19, 19, 20, 21, 22, 23, 24, 24, 24, 24, 24, 24, 25, 26, 27, 28, 29, 30, 30, 30, 30, 30, 31, 32, 33, 34, 35, 36, 37, 37, 37, 37, 38, 39, 40

Offset

0,2

Links

Table of n, a(n) for n=0..72.

Example

a(20) = 13 because there are 13 numbers in 0..20 whose digits are in nonincreasing order: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20.

Maple

a:= proc(n) option remember; `if`(n<0, 0, a(n-1)+`if`(
     (l-> is(l=sort(l)))(convert(n, base, 10)), 1, 0))
    end:
seq(a(n), n=0..72);  # Alois P. Heinz, Sep 12 2022

Mathematica

Accumulate @ Table[If[GreaterEqual @@ IntegerDigits[n], 1, 0], {n, 0, 72}] (* Amiram Eldar, Sep 10 2022 *)

Prog

(PARI) a(n) = sum(k=0, n, my(d=digits(k)); d == vecsort(d, , 4)); \\ Michel Marcus, Sep 10 2022

Crossrefs

Cf. A009996.

Sequence in context: A327886 A331166 A304232 * A303219 A071523 A297244

Adjacent sequences: A357027 A357028 A357029 * A357031 A357032 A357033

Keyword

nonn,base

Author

Osman Mustafa Quddusi, Sep 09 2022

Status

approved