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 A056812 #16 Aug 03 2017 04:16:22
%S A056812 0,1,2,1,2,2,3,3,2,2,3,3,4,4,4,4,5,5,6,6,6,6,7,7,6,6,6,6,7,7,8,8,8,8,
%T A056812 8,8,9,9,9,9,10,10,11,11,11,11,12,12,11,11,11,11,12,12,12,12,12,12,13,
%U A056812 13,14,14,14,14,14,14,15,15,15,15,16,16,17,17,17,17,17,17,18,18,18,18,19
%N A056812 Number of unitary prime factors of lcm[1..n], i.e., primes in LCM with exponent 1.
%C A056812 Number of primes in the interval ]sqrt(n), n], (i.e., excluding sqrt(n) but including n). - _Lekraj Beedassy_, Mar 31 2005
%H A056812 G. C. Greubel, <a href="/A056812/b056812.txt">Table of n, a(n) for n = 1..1000</a>
%F A056812 a(n) = A056169(A003418(n)).
%F A056812 a(n) = primepi(n) - primepi(sqrt(n)).
%F A056812 a(n) = A000720(n) - primepi(sqrt(n)).
%F A056812 a(n) = A001221(A003418(n)) - A000720(A000196(n)).
%e A056812 n=100, lcm(100) has 25 prime factors of which only 2 and 3 have exponent larger than 1; resulting powers: 64 and 81. So 23 prime factors are unitary, i.e., with exponent 1, so a(100)=23.
%t A056812 Join[{0}, Table[Count[Transpose[FactorInteger[Product[Cyclotomic[k, 1], {k, 2, n}]]][[2]], 1], {n, 2, 100}]] (* _G. C. Greubel_, May 13 2017 *)
%o A056812 (PARI) for(n=1,100, print1(primepi(n) - primepi(sqrt(n)), ", ")) \\ _G. C. Greubel_, May 13 2017
%Y A056812 Cf. A000196, A000720, A001221, A003418, A056169.
%K A056812 nonn
%O A056812 1,3
%A A056812 _Labos Elemer_, Aug 28 2000