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 A130859 #19 Jul 09 2025 04:27:16 %S A130859 1,1729,5184,10366,17275,25911,36274,48364,62181,77725,94996,113994, %T A130859 134719,157171,181350,207256,234889,264249,295336,328150,362691, %U A130859 398959,436954,476676,518125,561301,606204,652834,701191,751275,803086,856624,911889,968881,1027600,1088046,1150219 %N A130859 1729-gonal numbers. %H A130859 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1). %F A130859 a(n) = (1727*n^2 - 1725*n)/2. %F A130859 From _Elmo R. Oliveira_, Nov 27 2024: (Start) %F A130859 G.f.: x*(1 + 1726*x)/(1-x)^3. %F A130859 E.g.f.: exp(x)*x*(2 + 1727*x)/2. %F A130859 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 3. (End) %t A130859 PolygonalNumber[1729,Range[40]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Sep 15 2016 *) %o A130859 (PARI) a(n) = (1727*n^2 - 1725*n)/2 \\ _Michel Marcus_, Jul 16 2013 %Y A130859 Cf. A130876. %K A130859 nonn,easy %O A130859 1,2 %A A130859 _N. J. A. Sloane_, Oct 06 2007, based on a suggestion from Anton Mravcek in 2004