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 A291307 #12 Jan 16 2025 02:38:45
%S A291307 0,0,1,2,0,3,3,3,4,5,3,6,6,6,7,8,6,9,9,9,10,11,9,12,12,12,13,14,12,15,
%T A291307 15,15,16,17,15,18,18,18,19,20,18,21,21,21,22,23,21,24,24,24,25,26,24,
%U A291307 27,27,27,28,29,27,30,30,30,31,32,30,33,33,33,34
%N A291307 The arithmetic function v_6(n,2).
%D A291307 J. Butterworth, Examining the arithmetic function v_g(n,h). Research Papers in Mathematics, B. Bajnok, ed., Gettysburg College, Vol. 8 (2008).
%H A291307 Bela Bajnok, <a href="https://arxiv.org/abs/1705.07444">Additive Combinatorics: A Menu of Research Problems</a>, arXiv:1705.07444 [math.NT], May 2017. See Table in Section 1.6.1.
%F A291307 a(n) = (n-gcd(n,6))/2 = A291306(n)/2. - _Ridouane Oudra_, Jan 09 2025
%F A291307 Sum_{n>=7} (-1)^n/a(n) = Pi/(3*sqrt(3)) - 1/2. - _Amiram Eldar_, Jan 15 2025
%p A291307 seq((n-gcd(n,6))/2, n=2..80); # _Ridouane Oudra_, Jan 09 2025
%t A291307 v[g_, n_, h_] := (d = Divisors[n]; Max[(Floor[(d - 1 - GCD[d, g])/h] + 1)*n/d]); Table[v[6, n, 2], {n, 2, 70}]
%Y A291307 Cf. A289435, A289436, A289437, A289438, A289439, A289440, A289441.
%Y A291307 Cf. A291306.
%K A291307 nonn
%O A291307 2,4
%A A291307 _Robert Price_, Aug 21 2017