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 A227026 #17 Jul 30 2025 19:47:28
%S A227026 3,5,6,7,11,14,15,58,85,493,638,2871,16731,97513,568345,3312555,
%T A227026 19306983,112529341,655869061,3822685023,22280241075,129858761425,
%U A227026 756872327473,4411375203411,25711378892991,149856898154533,873430010034205,5090723162050695
%N A227026 Numbers k such that k!/m! is a triangular number for some m < k-1.
%C A227026 A011900 is a subsequence, except A011900(0)=1.
%C A227026 According to Melissen's comment in A097571, m > k-7.
%H A227026 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-7,1).
%F A227026 a(n) = 7a(n-1) - 7a(n-2) + a(n-3) for n > 14. - _Charles R Greathouse IV_, Jun 28 2013
%F A227026 G.f.: x * (3 -16*x -8*x^2 -3*x^3 -x^4 -20*x^5 -13*x^6 +40*x^7 -230*x^8 +289*x^9 -2276*x^10 +1771*x^11 +607*x^12 -145*x^13) / ((1-x)*(1-6*x+x^2)). - _Bruno Berselli_, Jun 28 2013
%t A227026 CoefficientList[Series[(3 - 16 x - 8 x^2 - 3 x^3 - x^4 - 20 x^5 - 13 x^6 + 40 x^7 - 230 x^8 + 289 x^9 - 2276 x^10 + 1771 x^11 + 607 x^12 - 145 x^13) / ((1 - x) (1 - 6 x + x^2)), {x, 0, 30}], x] (* _Bruno Berselli_, Jun 28 2013 *)
%Y A227026 Cf. A000217, A011900, A097571.
%K A227026 nonn,easy
%O A227026 1,1
%A A227026 _Alex Ratushnyak_, Jun 27 2013