A069654 a(1) = 1; for n > 1, a(n) = smallest number > a(n-1) having exactly n divisors.

1, 2, 4, 6, 16, 18, 64, 66, 100, 112, 1024, 1035, 4096, 4288, 4624, 4632, 65536, 65572, 262144, 262192, 263169, 269312, 4194304, 4194306, 4477456, 4493312, 4498641, 4498752, 268435456, 268437200, 1073741824, 1073741830, 1088472064, 1089142784, 1107225625

Offset

1,2

Links

Jon E. Schoenfield, Table of n, a(n) for n = 1..100 (first 83 terms from Charles R Greathouse IV)

Prog

(PARI) print(1" "1); N=1; for(n=2, 28, while(numdiv(N)!=n, N++); print(n" "N)) \\ Charles R Greathouse IV, Sep 08 2021
(Python)
from sympy import divisor_count
from itertools import count, islice
def agen(an=1, startn=1):
    for n in count(startn):
        while divisor_count(an) != n: an += 1
        yield an
print(list(islice(agen(), 22))) # Michael S. Branicky, Jan 16 2022

Crossrefs

Cf. A002182, A005179.

If "exactly" is changed to "at least", we get A072121.

Sequence in context: A114874 A100361 A259939 * A330359 A000068 A067662

Adjacent sequences: A069651 A069652 A069653 * A069655 A069656 A069657

Keyword

nonn

Author

Amarnath Murthy, Apr 04 2002

Extensions

Corrected and extended by Vladeta Jovovic, Jun 19 2002

More terms from David Wasserman, Apr 21 2003

a(25)-a(28) corrected by Charles R Greathouse IV, Sep 14 2021

Status

approved