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 A136684 #15 Feb 16 2025 08:33:07
%S A136684 3,5,8,11,20,38,61,65,71,80,83,93,233,704,1649,2909,3417,3634,9371
%N A136684 Numbers k such that A120296(k) is prime.
%C A136684 A120296(k) = Numerator of Sum_{j=1..k} (-1)^(j+1)/j^4.
%H A136684 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HarmonicNumber.html">Harmonic Number</a>
%t A136684 Do[ f=Numerator[ Sum[ (-1)^(k+1)*1/k^4, {k,1,n} ] ]; If[ PrimeQ[f], Print[ {n,f} ] ], {n,1,100} ]
%t A136684 Select[Range[1000],PrimeQ[Numerator[Sum[(-1)^(k+1) 1/k^4,{k,#}]]]&] (* _Harvey P. Dale_, Aug 28 2012 *)
%Y A136684 Cf. A058313, A119682, A136675, A120296, A136676, A136677.
%Y A136684 Cf. A001008, A007406, A007408, A007410, A099828, A103345.
%Y A136684 Cf. A136681, A136682, A136683, A136685, A136686.
%K A136684 nonn,more
%O A136684 1,1
%A A136684 _Alexander Adamchuk_, Jan 16 2008
%E A136684 More terms from _Harvey P. Dale_, Aug 28 2012
%E A136684 a(15)-a(19) from _Robert Price_, Apr 23 2019