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 A291515 #7 Jun 11 2025 00:58:36
%S A291515 -17,-17,-19,-17,-17,-19,-17,-17,-19,-20,-22,-24,-26,-28,-30,-32,-34,
%T A291515 -36,-38,-40,-42,-44,-46,-48,-50,-52,-54,-56,-58,-60,-62,-64,-66,-68,
%U A291515 -70,-72,-74,-76,-78,-80,-82,-84,-86,-88,-90,-92,-94,-96,-98,-100,-102,-104,-106,-108,-110,-112,-114,-116,-118,-120,-122,-124,-126,-128,-130,-132,-134,-136,-138,-140
%N A291515 The arithmetic function uhat(n,3,6).
%H A291515 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 1.6.4.
%F A291515 Conjectures from _Chai Wah Wu_, Jun 10 2025: (Start)
%F A291515 a(n) = 2*a(n-1) - a(n-2) for n > 11.
%F A291515 G.f.: x*(-x^10 + x^9 - 2*x^8 - 2*x^7 + 4*x^6 - 2*x^5 - 2*x^4 + 4*x^3 - 2*x^2 + 17*x - 17)/(x - 1)^2. (End)
%t A291515 delta[r_, k_, d_] := If[r < k, (k - r)*r - (d - 1), If[k < r && r < d, (d - r)*(r - k) - (d - 1), If[k == r && r == d, d - 1, 0]]] uhat[n_, m_, h_] := (dx = Divisors[n]; dmin = n; For[i = 1, i ≤ Length[dx], i++, d = dx[[i]]; k = m - d*Ceiling[m/d] + d; r = h - d*Ceiling[h/d] + d; If[h ≤ Min[k, d - 1], dmin = Min[dmin, n, (h*Ceiling[m/d] - h + 1)*d, h*m - h*h + 1], dmin = Min[dmin, n, h*m - h*h + 1 - delta[r, k, d]]]]; dmin) Table[uhat[n, 3, 6], {n, 1, 70}]
%Y A291515 Cf. A289435, A289436, A289437, A289438, A289439, A289440, A289441.
%K A291515 sign
%O A291515 1,1
%A A291515 _Robert Price_, Aug 25 2017