A385494 Total number of 1's in the decimal digits of the divisors of n.

1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 1, 2, 1, 2, 1, 2, 1, 3, 2, 2, 3, 2, 1, 3, 1, 2, 2, 2, 2, 3, 1, 3, 2, 1, 1, 3, 1, 2, 3, 2, 1, 2, 3, 2, 2, 1, 1, 4, 2, 2, 2, 2, 2, 3, 1, 2, 1, 3, 2, 3, 1, 1, 2, 2, 3, 2, 1, 3, 2, 2, 1, 4, 2, 1, 1, 3, 1, 4, 3, 1, 2, 1, 2, 3, 1, 2, 3, 3

Offset

1,10

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(11) = 3 because of the divisors of 11, there is one 1 in 1 and two in 11.
a(60) = 4 because of the divisors of 60, there is one 1 in 1, one in 10, one in 12, one in 15 and none in the other divisors.

Maple

f:= proc(n) local d; add(numboccur(1, convert(d, base, 10)), d=numtheory:-divisors(n)) end proc:
map(f, [$1..100]);

Mathematica

a[n_]:=Count[IntegerDigits[Divisors[n]]//Flatten, 1]; Array[a, 100] (* Stefano Spezia, Aug 28 2025 *)

Prog

(Python)
from sympy import divisors
def a(n): return sum(str(d).count("1") for d in divisors(n, generator=True))
print([a(n) for n in range(1, 101)]) # Michael S. Branicky, Aug 27 2025
(PARI) a(n) = sumdiv(n, d, #select(x->(x==1), digits(d))); \\ Michel Marcus, Aug 28 2025

Crossrefs

Cf. A093653, A387357.

Sequence in context: A120881 A297930 A031217 * A064131 A368859 A338238

Adjacent sequences: A385491 A385492 A385493 * A385495 A385496 A385497

Keyword

nonn,base

Author

Robert Israel, Aug 27 2025

Status

approved