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 A064167 #14 May 01 2022 11:21:26 %S A064167 1,6,66,300,8220,980,50820,213080,17965080,18600120,2320468920, %T A064167 2384502120,412970037480,422245703880,430902992520,1756076802480, %U A064167 516336630329520,58297387228080,21362271268818480,866533600973040,97555876321904,98772315738096,52866073370045936,481103506052529360 %N A064167 Product of numerator and denominator of the n-th harmonic number, 1 + 1/2 + 1/3 +...+ 1/n. %C A064167 Numerator and denominator in definition have no common divisors >1. %H A064167 Harvey P. Dale, <a href="/A064167/b064167.txt">Table of n, a(n) for n = 1..1000</a> %e A064167 The 3rd harmonic number is 11/6. So a(3) = 11 * 6 = 66. %t A064167 Numerator[#]Denominator[#]&/@HarmonicNumber[Range[30]] (* _Harvey P. Dale_, May 01 2022 *) %o A064167 (PARI) a(n) = my(h=sum(k=1, n, 1/k)); numerator(h) * denominator(h); \\ _Michel Marcus_, Sep 07 2019 %Y A064167 Cf. A001008, A002805, A064168, A064169. %K A064167 nonn %O A064167 1,2 %A A064167 _Leroy Quet_, Sep 19 2001 %E A064167 More terms from _Michel Marcus_, Sep 07 2019