cp's OEIS Frontend

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.

A077649 Initial digit of composite numbers.

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%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