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 A038838 #50 Nov 21 2020 03:36:42
%S A038838 9,18,25,27,36,45,49,50,54,63,72,75,81,90,98,99,100,108,117,121,125,
%T A038838 126,135,144,147,150,153,162,169,171,175,180,189,196,198,200,207,216,
%U A038838 225,234,242,243,245,250,252,261,270,275,279,288,289,294,297,300,306
%N A038838 Numbers that are divisible by the square of an odd prime.
%C A038838 Condition 1 of Theorem 7.5 (Robinson, 1979) includes: "k is a multiple of a square of an odd prime." - _Jonathan Vos Post_, Aug 06 2007
%C A038838 If m is a term, every k*m with k > 1 is another term and the primitive terms are the square of odd primes. The subsequence of odd terms is A053850 while the even terms 18, 36, 50, 54, 72, 90, 98, ... are exactly twice the terms of this sequence. - _Bernard Schott_, Nov 20 2020
%C A038838 The asymptotic density of this sequence is 1 - 8/Pi^2 = 0.189430... - _Amiram Eldar_, Nov 21 2020
%H A038838 Reinhard Zumkeller, <a href="/A038838/b038838.txt">Table of n, a(n) for n = 1..10000</a>
%H A038838 M. Beeler, R. W. Gosper, and R. Schroeppel, <a href="http://www.inwap.com/pdp10/hbaker/hakmem/number.html#item45">HAKMEM ITEM 45</a>.
%H A038838 Raphael M. Robinson, <a href="https://doi.org/10.1007/BF01214145">Multiple tiling of n-dimensional space by unit cubes</a>, Math. Z., Vol. 166 (1979), pp. 225-264.
%H A038838 Chuanming Zong, <a href="http://dx.doi.org/10.1090/S0273-0979-05-01050-5">What is known about unit cubes</a>, Bull. Amer. Math. Soc., Vol. 42, No. 2 (2005), pp. 181-211; Robinson theorem cited on p. 204.
%F A038838 {a(n)} = {j such that for some k>1 A001248(k)|j} = {j such that for some k>0 (A065091(k)^2)|j}. - _Jonathan Vos Post_, Aug 06 2007
%F A038838 A008966(A000265(a(n))) = 0. - _Reinhard Zumkeller_, Nov 08 2009
%o A038838 (PARI) {a(n) = my(m, c); if( n<1, 0, c=0; m=0; while( c<n, m++; if( moebius(m / 2^valuation(m, 2))==0, c++)); m)}; /* _Michael Somos_, Aug 22 2006 */
%o A038838 (PARI) list(lim)=my(v=List(),n,e,t); forfactored(k=9,lim\1, e=k[2][,2]; t=#e; n=k[1]; if(if(n%2 && t, vecmax(e)>1, t>1, vecmax(e[2..t])>1, 0), listput(v, k[1]))); Vec(v) \\ _Charles R Greathouse IV_, Jan 08 2018
%Y A038838 Cf. A000040, A065091, A122132 (complement).
%Y A038838 Cf. A013929 (supersequence of nonsquarefrees).
%Y A038838 Subsequences: A001248 \ {2} (primitives), A053850 (odds), A036785 (divisible by the squares of two distinct primes).
%Y A038838 Subsequence of A167662. - _Reinhard Zumkeller_, Nov 08 2009
%K A038838 nonn
%O A038838 1,1
%A A038838 _David W. Wilson_