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 A141551 #7 Jul 08 2019 12:28:54 %S A141551 1,2,4,6,12,24,36,48,60,72,84,96,108,120,132,144,156,180,192,204,228, %T A141551 240,252,276,288,300,324,348,360,372,396,444,468,480,492,516,564,576, %U A141551 588,600,612,636,684,708,720,732,804,828,840,852,876,900,948,960,972,996,1044,1068 %N A141551 Numbers k with property that if d divides k, then tau(tau(d)) also divides k. %C A141551 tau() = A000005(). %H A141551 Amiram Eldar, <a href="/A141551/b141551.txt">Table of n, a(n) for n = 1..10000</a> %p A141551 with(numtheory); isA141551 := proc(n) local dvs,d; dvs := divisors(n) ; for d in dvs do if not tau(tau(d)) in dvs then RETURN(false): fi; od: RETURN(true); end: %p A141551 t1:=[]; for n from 1 to 60000 do if isA141551(n) then t1:=[op(t1),n]; fi; od: %t A141551 aQ[n_] := AllTrue[Divisors[n], Divisible[n, DivisorSigma[0, DivisorSigma[0, #]]] &]; Select[Range[1000], aQ] (* _Amiram Eldar_, Jul 08 2019 *) %Y A141551 Cf. A000005, A010553, A141586. %K A141551 nonn %O A141551 1,2 %A A141551 _N. J. A. Sloane_, Sep 12 2008