A376800 3-brilliant numbers with distinct prime factors.
30, 42, 70, 105, 2431, 2717, 3289, 3553, 4147, 4199, 4301, 4433, 4807, 5083, 5291, 5423, 5681, 5797, 5863, 6061, 6149, 6409, 6479, 6721, 6851, 6919, 7163, 7337, 7429, 7579, 7657, 7667, 7733, 7843, 8041, 8177, 8437, 8569, 8671, 8723, 8789, 8987, 9061, 9139, 9269
Offset: 1
Examples
30 = 2*3*5 is a term. 2431 = 11*13*17 is a term.
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..10000
Programs
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Python
from sympy import factorint def ok(n): f = factorint(n) return len(f) == sum(f.values()) == 3 and len(set([len(str(p)) for p in f])) == 1 print([k for k in range(9300) if ok(k)]) # Michael S. Branicky, Oct 05 2024 -
Python
from math import prod from sympy import primerange from itertools import count, combinations, islice def bgen(d): # generator of terms that are products of d-digit primes primes, out = list(primerange(10**(d-1), 10**d)), set() for t in combinations(primes, 3): out.add(prod(t)) yield from sorted(out) def agen(): # generator of terms for d in count(1): yield from bgen(d) print(list(islice(agen(), 45))) # Michael S. Branicky, Oct 05 2024
Extensions
a(6) and beyond from Michael S. Branicky, Oct 05 2024