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 A098241 #22 Jun 05 2025 23:32:37
%S A098241 302,2117,2909,3327,3932,5142,5747,6957,8772,9377,11192,12402,13007,
%T A098241 14217,14547,16032,17847,18452,20267,20366,21477,22082,23292,23897,
%U A098241 25107,25403,26922,27527,29342,30552,31157,32367,32972,34182,35997,36602,37823,38417,39627
%N A098241 Numbers k such that 216*k+108 is a term of A097703 and A007494 and A098240.
%C A098241 Numbers k such that m = 216*k+108 satisfies sigma(m) <> 2*usigma(m) (A097703), m is not of the form 3x+1 (A007494) and GCD(2*m+1, numerator(Bernoulli(4*m+2))) is squarefree (A098240).
%C A098241 Also, terms m of A097704 such that GCD(2*m+1, Bernoulli(4*m+2)) is squarefree. Most terms of A097704 are in A098240. These are the exceptions.
%H A098241 Amiram Eldar, <a href="/A098241/b098241.txt">Table of n, a(n) for n = 1..100</a>
%t A098241 usigma[n_] := Block[{d = Divisors[n]}, Plus @@ Select[d, GCD[ #, n/# ] == 1 &]]; lmt = 1296000; t = (Select[ Range[ lmt], DivisorSigma[1, # ] == 2usigma[ # ] &] - 108)/216; u = (Select[ Range[ Floor[(lmt - 108)/432]], !SquareFreeQ[ GCD[ #, Numerator[ BernoulliB[ 2# ]] ]] &] -1)/2; v = Table[ 3k - 2, {k, Floor[(lmt - 108)/216]}]; Complement[ Range[ Floor[ (lmt - 108)/216]], t, u, v]
%t A098241 q[n_] := Mod[n, 3] != 1 && (Divisible[2*n + 1, 3] || (! Divisible[2*n + 1, 3] && ! SquareFreeQ[2*n + 1])) && SquareFreeQ[GCD[2*n + 1, BernoulliB[4*n + 2]]]; Select[Range[10^4], q] (* _Amiram Eldar_, Aug 31 2024 *)
%Y A098241 Cf. A000203, A034448, A007494, A016777, A027641, A027642, A063880, A067778, A097703, A097704, A098240.
%K A098241 nonn
%O A098241 1,1
%A A098241 _Ralf Stephan_ and _Robert G. Wilson v_, Sep 15 2004
%E A098241 More terms from _Amiram Eldar_, Aug 31 2024