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 A079123 #16 Jul 21 2025 21:40:58 %S A079123 0,0,0,0,0,0,0,0,0,0,1,1,2,1,0,3,3,1,1,0,2,4,5,2,2,4,2,1,8,3,7,9,4,4, %T A079123 6,5,3,8,2,8,3,9,6,4,6,8,7,7,4,12,4,15,10,10,9,13,10,15,7,7,19,15,9, %U A079123 20,12,11,12,15,19,12,15,20,10,12,13,13,19,16,13,21,17,17,23,19,13,13,15,18,20,16,27 %N A079123 Number of 4's in n# (n primorial) = 4's in A002110(n). %H A079123 Alois P. Heinz, <a href="/A079123/b079123.txt">Table of n, a(n) for n = 0..10000</a> (999 terms from Vincenzo Librandi) %t A079123 Count[IntegerDigits[#], 4]&/@FoldList[Times, 1, Prime[Range[90]]] (* _Harvey P. Dale_, Oct 12 2011 *) %o A079123 (PARI) \\ See program in A079099. %Y A079123 Cf. A002110, A079099. %K A079123 nonn,base,easy %O A079123 0,13 %A A079123 _Cino Hilliard_, Feb 03 2003 %E A079123 Offset corrected by _Alois P. Heinz_, Jul 21 2025