This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A370680 #14 Feb 29 2024 16:18:08 %S A370680 6,1026,120878,13234670,1383218064,140953635171 %N A370680 a(n) is the number of pairs x <= y of n-digit numbers such that the number of distinct digits in their product is greater than in their concatenation. %e A370680 a(1) = 6: 6 squares 4*4, ..., 9*9 with 2 distinct digits in x*y = 16, 25, ..., and 1 digit in their concatenation. %o A370680 (PARI) See A370678. %o A370680 (Python) %o A370680 def A370680(n): %o A370680 a = 10**(n-1) %o A370680 b, c = 10*a, 0 %o A370680 for x in range(a,b): %o A370680 s = set(str(x)) %o A370680 for y in range(x,b): %o A370680 if len(s|set(str(y))) < len(set(str(x*y))): %o A370680 c += 1 %o A370680 return c # _Chai Wah Wu_, Feb 28 2024 %Y A370680 Cf. A370675, A370676, A370678, A370679. %K A370680 nonn,base,more %O A370680 1,1 %A A370680 _Hugo Pfoertner_, Feb 26 2024 %E A370680 a(6) from _Martin Ehrenstein_, Feb 29 2024