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 A191599 #33 Feb 01 2022 00:28:28 %S A191599 11,13,17,19,22,23,26,29,31,33,34,37,38,39,41,43,44,46,47,51,52,53,55, %T A191599 57,58,59,61,62,65,66,67,68,69,71,73,74,76,77,78,79,82,83,85,86,87,89, %U A191599 93,94,95,97,99,101,102,103,104,106,107,109,110,111,113,114 %N A191599 Numbers k that do not divide Ramanujan's tau(k). %C A191599 This sequence has its first 45 terms in common with A068191. %C A191599 Subsequence of A068191. %C A191599 Complement of A063938. - _Omar E. Pol_, Aug 28 2011 %H A191599 T. D. Noe, <a href="/A191599/b191599.txt">Table of n, a(n) for n = 1..1000</a> %H A191599 B. Ramakrishnan and Brundaban Sahu, <a href="https://arxiv.org/abs/0711.3512">Rankin-Cohen brackets and Van der Pol-type identities for the Ramanujan's tau function</a>, arXiv:0711.3512 [math.NT], 2007, pp. 14. See Corollary 2.11 %e A191599 For n=1, a(1)=11 since 11 does not divide tau(11) = 534612. %p A191599 with(numtheory): tn := proc(n) modp(-840*sum(k^4*sigma(k)*sigma(n-k),k=1..n-1),n); end; ser := proc(a,b) local n,lis; lis := []; for n from a to b do if tn(n) <> 0 then lis := [op(lis),n]; fi; od; lis; end; %t A191599 Select[Range[120], !Divisible[RamanujanTau[#], #]&] (* _Jean-François Alcover_, Nov 29 2017 *) %o A191599 (PARI) isok(k) = ramanujantau(k) % k; \\ _Michel Marcus_, Aug 14 2021 %Y A191599 Cf. A000594, A068191. %K A191599 nonn %O A191599 1,1 %A A191599 _Luis H. Gallardo_, Jun 08 2011