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 A038800 #37 May 04 2025 12:26:11
%S A038800 4,4,2,2,3,2,2,3,2,1,4,1,1,3,1,2,2,2,1,4,0,1,3,2,1,2,2,2,2,1,1,3,0,2,
%T A038800 2,2,1,2,2,1,2,1,1,3,2,1,3,1,1,2,2,0,2,0,2,1,2,2,1,2,2,3,0,1,3,2,1,2,
%U A038800 1,1,2,1,1,2,1,2,2,1,1,1,1,1,4,1,0,3,1,1,3,0,1,2,1,1,2,1,1,2,1,2,1,2,1,3,1,1
%N A038800 Number of primes between 10n and 10n+9.
%C A038800 If n runs through the primes, the subsequence 2, 2, 2, 3, 1, 3, 2, 4, 2, 1, 3, 2, 1, 3, 1, 0, 2, 3, 2,... is created. - _R. J. Mathar_, Jul 19 2012
%C A038800 Since 431, 433, and 439 are all prime, a(43)=3. - _Bobby Jacobs_, Sep 25 2016
%H A038800 Michael De Vlieger, <a href="/A038800/b038800.txt">Table of n, a(n) for n = 0..10000</a>
%H A038800 A. Frank and P. Jacqueroux, <a href="http://www.paulcooijmans.com/others/intcontest.pdf">International Contest</a>, 2001. Numerators of Item 23
%t A038800 Table[Count[Range[10 n, 10 n + 9], p_ /; PrimeQ@ p], {n, 0, 105}] (* _Michael De Vlieger_, Sep 25 2016 *)
%t A038800 Table[PrimePi[10n+9]-PrimePi[10n],{n,0,120}] (* _Harvey P. Dale_, May 04 2025 *)
%o A038800 (PARI) a(n) = primepi(10*n+9) - primepi(10*n); \\ _Michel Marcus_, Sep 26 2016
%Y A038800 Cf. A055781, A055782, A055783, A055784.
%Y A038800 Positions of 4's: {0} U A007811.
%Y A038800 Cf. A098592.
%K A038800 easy,nonn
%O A038800 0,1
%A A038800 _Jeff Burch_
%E A038800 a(43) corrected by _Bobby Jacobs_, Sep 25 2016
%E A038800 a(101) and a(104) corrected by _Michael De Vlieger_, Sep 25 2016