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 A077649 #13 Dec 13 2017 02:44:12 %S A077649 4,6,8,9,1,1,1,1,1,1,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,5, %T A077649 5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,9,9,9,9, %U A077649 9,9,9,9,9,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 %N A077649 Initial digit of composite numbers. %F A077649 a(n) = A000030(A002808(n)). %t A077649 c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[First[IntegerDigits[c[w]]], {w, 1, 128}] %t A077649 First[IntegerDigits[#]]&/@Complement[Range[150],Prime[Range[ PrimePi[150]]]] (* _Harvey P. Dale_, Apr 26 2011 *) %o A077649 (PARI) lista(nn) = forcomposite(n=1, nn, print1(digits(n)[1], ", ")); \\ _Michel Marcus_, Dec 13 2017 %Y A077649 Cf. A000030, A002808, A077648. %K A077649 base,easy,nonn %O A077649 1,1 %A A077649 _Labos Elemer_, Nov 19 2002