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 A048544 #21 Feb 16 2025 08:32:40
%S A048544 72,11772,771762,757770,77677782,779777700,7077772770,778777127772,
%T A048544 7777770777090,57777777767730,7777577077877756,177677777977777980,
%U A048544 17673737777477771772,677777977779775677756,1789771777777771777710,7747977777770507777772,298777877777767737777770
%N A048544 Smallest oblong (promic) number containing exactly n 7's.
%H A048544 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PronicNumber.html">Pronic Number</a>
%t A048544 With[{pn=2*Accumulate[Range[430000000]]},Table[Select[pn,DigitCount[#,10,7] == n&,1],{n,12}]]//Flatten (* _Harvey P. Dale_, Aug 14 2017 *)
%o A048544 (Python)
%o A048544 def A048544(n):
%o A048544 k, m = 1, 2
%o A048544 while True:
%o A048544 if str(m).count('7') == n:
%o A048544 return m
%o A048544 k += 1
%o A048544 m += 2*k # _Chai Wah Wu_, Mar 23 2018
%Y A048544 Cf. A048543, A002378.
%Y A048544 Cf. A048530, A048532, A048534, A048536, A048538, A048540, A048542, A048546, A048548.
%K A048544 nonn,base
%O A048544 1,1
%A A048544 _Patrick De Geest_, May 15 1999
%E A048544 a(13)-a(17) from _Giovanni Resta_, Oct 09 2019