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 A316865 #11 Aug 11 2018 14:08:07 %S A316865 0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0, %T A316865 1,0,0,0,0,0,1,1,1,1,2,1,1,1,1,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0, %U A316865 0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1 %N A316865 Number of times 4 appears in decimal expansion of n. %e A316865 a(0) = 0 since the decimal representation of 0 does not contain the digit 4. %e A316865 a(4) = 1 since 4 appears once in the decimal expansion of 4. %t A316865 Array[ DigitCount[#, 10, 4] &, 105, 0] %o A316865 (PARI) a(n) = #select(x->x==4, digits(n)); \\ _Michel Marcus_, Jul 20 2018 %Y A316865 Cf. A043505, A043506, A043507, A043508. %Y A316865 Cf. A055641, A268643, A316863, A316864, A316866, A316867, A316868, A316869, A102683. %K A316865 base,easy,nonn %O A316865 0,45 %A A316865 _Robert G. Wilson v_, Jul 15 2018