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A368955 Numbers that are the product of two repdigit numbers.

%I A368955 #19 Jan 12 2024 22:24:48
%S A368955 0,1,2,3,4,5,6,7,8,9,10,11,12,14,15,16,18,20,21,22,24,25,27,28,30,32,
%T A368955 33,35,36,40,42,44,45,48,49,54,55,56,63,64,66,72,77,81,88,99,110,111,
%U A368955 121,132,154,165,176,198,220,222,231,242,264,275,297,308,330,333
%N A368955 Numbers that are the product of two repdigit numbers.
%C A368955 A010785 and A368944 are subsequences.
%C A368955 Numbers of the form i*j*(10^k - 1)*(10^m - 1)/81 where 0 <= i, j <= 9 and k, m >= 0.
%F A368955 a(n) = A140332(n) for n <= 46.
%t A368955 repQ[n_] := SameQ @@ IntegerDigits[n]; q[n_] := AnyTrue[Divisors[n], repQ[#] && repQ[n/#] &]; q[0] = True; Select[Range[0, 333], q] (* _Amiram Eldar_, Jan 12 2024 *)
%o A368955 (Python)
%o A368955 from itertools import count, takewhile
%o A368955 def repdigits():
%o A368955     yield 0
%o A368955     yield from ((10**d-1)//9*i for d in count(1) for i in range(1, 10))
%o A368955 def aupto(LIMIT): # use LIMIT = 10**34 for 10K+-term b-file
%o A368955     s, R = set(), list(takewhile(lambda x:x<=LIMIT, repdigits()))
%o A368955     for i, r1 in enumerate(R):
%o A368955         for r2 in R[i:]:
%o A368955             p = r1*r2
%o A368955             if p > LIMIT: break
%o A368955             s.add(p)
%o A368955     return sorted(s)
%o A368955 print(aupto(333)) # _Michael S. Branicky_, Jan 10 2024
%Y A368955 Cf. A002283, A010785, A140332, A368944.
%K A368955 nonn,base,easy
%O A368955 1,3
%A A368955 _Stefano Spezia_, Jan 10 2024