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 A085981 #12 Oct 30 2023 09:52:24 %S A085981 0,0,0,1,0,0,1,0,0,0,0,1,0,0,1,0,0,0,1,1,1,1,0,0,1,0,0,1,0,0,1,0,1,0, %T A085981 0,0,1,0,1,1,1,0,0,0,1,0,0,0,1,0,0,0,0,0,1,0,0,1,2,0,0,0,1,0,0,1,0,1, %U A085981 1,0,0,0,1,1,1,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,1,1,1,0,0,0,0,0,0,0,1,1,0,0,1 %N A085981 Number of 7's in decimal expansion of prime(n). %H A085981 Reinhard Zumkeller, <a href="/A085981/b085981.txt">Table of n, a(n) for n = 1..10000</a> %t A085981 DigitCount[Prime[Range[100]],10,7] (* _Paolo Xausa_, Oct 30 2023 *) %o A085981 (Haskell) %o A085981 a085981 = count7 0 . a000040 where %o A085981 count7 c x | d == 7 = if x < 10 then c + 1 else count7 (c + 1) x' %o A085981 | otherwise = if x < 10 then c else count7 c x' %o A085981 where (x', d) = divMod x 10 %o A085981 -- _Reinhard Zumkeller_, Apr 08 2014 %Y A085981 Cf. 0's A085974, 1's A085975, 2's A085976, 3's A085977, 4's A085978, 5's A085979, 6's A085980, 8's A085982, 9's A085983. %K A085981 base,nonn %O A085981 1,59 %A A085981 _Jason Earls_, Jul 06 2003