OFFSET
1,10
COMMENTS
LINKS
Michel Marcus, Table of n, a(n) for n = 1..10000
EXAMPLE
The divisors of 26 that start in 2 are 2 and 26, so a(26) = 2.
MATHEMATICA
f[n_] := IntegerDigits[n][[1]]; a[n_] := DivisorSum[n, 1 &, f[#] == f[n] &]; Array[a, 100] (* Amiram Eldar, Sep 23 2022 *)
PROG
(PARI) a(n) = my(fd=digits(n)[1]); sumdiv(n, d, digits(d)[1] == fd); \\ Michel Marcus, Sep 23 2022
(Python)
from sympy import divisors
def a(n): f = str(n)[0]; return sum(1 for d in divisors(n) if str(d)[0]==f)
print([a(n) for n in range(1, 101)]) # Michael S. Branicky, Sep 23 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Bernard Schott, Sep 23 2022
STATUS
approved