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URL: https://oeis.org/A388296

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A388296
Smallest k for which A389781(k) = n.
0
1, 2, 12, 6, 30, 42, 273, 330, 510, 210, 2310, 7854, 14790, 36465, 39270, 46410, 60060, 465465, 570570, 1411410, 1438710, 10010910, 7402395, 28393365, 20930910, 9699690, 23393370, 77087010, 117110994, 324939615, 179444265, 1048448310, 648858210, 577642065
OFFSET
1,2
FORMULA
a(n) >= A061799(n). - David A. Corneth, Oct 28 2025
MATHEMATICA
a389781[k_]:=Module[{d=Divisors[k]}, Count[PowerMod[d, k/d, k]-Mod[d, k], 0]]; a[n_]:=Module[{k=1}, While[a389781[k]!=n, k++]; k]; Array[a, 19] (* James C. McMahon, Nov 01 2025 *)
PROG
(Magma) [Min([k: k in [1..15000] | 1 + #[d: d in Divisors(k) | Modexp(d, k div d, k) mod k eq d] eq n]): n in [1..13]];
(Python)
from sympy import divisors
from itertools import count, islice
def f(n): return sum(1 for d in divisors(n, generator=True) if pow(d, n//d, n) == d%n)
def agen(): # generator of terms
adict, n = dict(), 1
for k in count(1):
v = f(k)
if v not in adict:
adict[v] = k
while n in adict: yield adict[n]; n += 1
print(list(islice(agen(), 19))) # Michael S. Branicky, Oct 28 2025
CROSSREFS
Sequence in context: A345469 A035877 A086494 * A354484 A107414 A133437
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(20)-a(34) from Michael S. Branicky, Oct 29 2025
STATUS
approved