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 A381248 #33 Feb 18 2025 22:42:49
%S A381248 1,4,14,156,20,750,1763,22142,77776,64420,2443077,52663933,227623468,
%T A381248 1097568095,3149642939,81965144711,105625962315,143416754568,
%U A381248 8084207326294,2574579252942508,14079288482520493,68732231173154643,33344665050312525,350798169613138819009,201175550741393337488
%N A381248 a(n) = least positive integer m such that m*(m+1) has n-2 distinct digits in base n, all distinct from those (base-n digits) of m and m+1.
%H A381248 Daniel Mondot, <a href="/A381248/b381248.txt">Table of n, a(n) for n = 2..45</a>
%e A381248 In base 3, 4*5 = 20 (11*12=202) which has one new digit, 0, that doesn’t exist in 4 or 5.
%e A381248 a(36) is 9725029095719647800676409109. It is XXXXXXXXXXXXXXXXXX in base 36, and XXXXXXXXXXXXXXXXXX * XXXXXXXXXXXXXXXXXY = W048CGKOSX159DHLPT3ZVRNJFB72YUQMIEA6. Every digit is present exactly once in the product. - _Daniel Mondot_, Feb 18 2025
%o A381248 (PARI) apply( {A381248(b=10)=for(n=b^abs(b\/2-1.5)\/1,oo, #setminus(Set(digits(n*(n+1),b)), Set(concat(digits(n,b), digits(n+1,b))))>b-3&&return(n))}, [2..10])
%Y A381248 Cf. A381247.
%K A381248 nonn,base
%O A381248 2,2
%A A381248 _Ali Sada_ and _M. F. Hasler_, Feb 17 2025
%E A381248 a(11)-a(16) from _Daniel Mondot_, Feb 17 2025
%E A381248 a(17)-a(26) from _Michael S. Branicky_, Feb 18 2025