cp's OEIS Frontend

A248410 a(n) = number of polynomials a_k*x^k + ... + a_1*x + n with k > 0, integer coefficients and only distinct integer roots.

%I A248410 #27 May 22 2025 10:21:40
%S A248410 3,11,11,23,11,43,11,47,23,43,11,103,11,43,43,83,11,103,11,103,43,43,
%T A248410 11,223,23,43,47,103,11,187,11,139,43,43,43,275,11,43,43,223,11,187,
%U A248410 11,103,103,43,11,427,23,103,43,103,11,223,43,223,43,43,11,503,11,43,103,227,43,187,11,103,43,187,11,635,11,43,103,103,43,187,11
%N A248410 a(n) = number of polynomials a_k*x^k + ... + a_1*x + n with k > 0, integer coefficients and only distinct integer roots.
%C A248410 If D_n is the set of all positive and negative divisors of n, then a(n) is the number of all subsets of D_n for which the product of all their elements is a divisor of n. a(n) depends only on the prime signature of n.
%H A248410 Reiner Moewald, <a href="/A248410/b248410.txt">Table of n, a(n) for n = 1..502</a>
%e A248410 a(1)=3: x + 1; -x + 1; -x^2 + 1.
%o A248410 (Python)
%o A248410 from itertools import chain, combinations
%o A248410 def powerset(iterable):
%o A248410    s = list(iterable)
%o A248410    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
%o A248410 print("Start")
%o A248410 a_n = 0
%o A248410 for num in range(1,1000):
%o A248410    div_set = set((-1,1))
%o A248410    a_n = 0
%o A248410    for divisor in range(1, num + 1):
%o A248410       if (num % divisor == 0):
%o A248410          div_set.add(divisor)
%o A248410          div_set.add(divisor*(-1))
%o A248410    pow_set = set(powerset(div_set))
%o A248410    num_set = len(pow_set)
%o A248410    for count_set in range(0, num_set):
%o A248410       subset = set(pow_set.pop())
%o A248410       num_subset = len(subset)
%o A248410       prod = 1
%o A248410       if num_subset < 1:
%o A248410          prod = 0
%o A248410       for count_subset in range (0, num_subset):
%o A248410          prod = prod * subset.pop()
%o A248410       if prod != 0:
%o A248410          if (num % prod == 0):
%o A248410             a_n = a_n +1
%o A248410    print(num, a_n)
%o A248410 print("Ende")
%Y A248410 Cf. A248348, A248955.
%K A248410 nonn
%O A248410 1,1
%A A248410 _Reiner Moewald_, Oct 06 2014