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A357429

Numbers whose digit representation in base 3 is equal to the digit representation in base 3 of the initial terms of their sets of divisors in increasing order.

1, 48, 50, 333, 438, 448, 734217, 6561081

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

In base 3, 48 is 1210 and its first divisors are 1, 2 and 3, that is, 1, 2 and 10.

PROG

(PARI) isok(k) = my(s=[]); fordiv(k, d, s=concat(s, digits(d, 3)); if (fromdigits(s, 3)==k, return(1)); if (fromdigits(s, 3)> k, return(0)));

(Python)

from sympy import divisors

from sympy.ntheory import digits

def ok(n):

target, s = "".join(map(str, digits(n, 3)[1:])), ""

if target[0] != "1": return False

for d in divisors(n):

s += "".join(map(str, digits(d, 3)[1:]))

if len(s) >= len(target): return s == target

elif not target.startswith(s): return False

print([k for k in range(10**5) if ok(k)]) # Michael S. Branicky, Oct 01 2022

CROSSREFS

Cf. A175252 (base 10), A357428 (base 2).

Sequence in context: A332242 A296872 A364702 * A258694 A328738 A067191

Adjacent sequences: A357426 A357427 A357428 * A357430 A357431 A357432

KEYWORD

nonn,base,more

AUTHOR

Michel Marcus, Sep 28 2022

STATUS

approved