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 A022269 #34 Feb 08 2025 19:33:38
%S A022269 0,6,23,51,90,140,201,273,356,450,555,671,798,936,1085,1245,1416,1598,
%T A022269 1791,1995,2210,2436,2673,2921,3180,3450,3731,4023,4326,4640,4965,
%U A022269 5301,5648,6006,6375,6755,7146,7548,7961,8385,8820,9266,9723,10191,10670,11160
%N A022269 a(n) = n*(11*n+1)/2.
%C A022269 Number of sets which can be obtained by selecting unique elements from two sets with 2n and 3n elements respectively and n common elements. - Dolmatov S. (aalma(AT)mail.ru), Jun 24 2003
%H A022269 G. C. Greubel, <a href="/A022269/b022269.txt">Table of n, a(n) for n = 0..5000</a>
%H A022269 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A022269 a(n) = A110449(n, 5) for n>4.
%F A022269 a(n) = 11*n + a(n-1) - 5 with n>0, a(0)=0. - _Vincenzo Librandi_, Aug 04 2010
%F A022269 G.f.: x*(6 + 5*x)/(1 - x)^3. - _Philippe Deléham_, Mar 27 2013
%F A022269 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) with n>2, a(0)=0, a(1)=6, a(2)=23. - _Philippe Deléham_, Mar 27 2013
%F A022269 a(n) = A218530(11*n+5).
%F A022269 a(n) = A000217(6*n) - A000217(5*n). - _Bruno Berselli_, Oct 13 2016
%F A022269 E.g.f.: (x/2)*(11*x + 12)*exp(x). - _G. C. Greubel_, Aug 24 2017
%t A022269 Table[n*(11*n + 1)/2, {n,0,50}] (* _G. C. Greubel_, Aug 24 2017 *)
%o A022269 (PARI) a(n)=n*(11*n+1)/2 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A022269 Cf. A110449.
%Y A022269 Cf. similar sequences listed in A022289.
%K A022269 nonn,easy
%O A022269 0,2
%A A022269 _N. J. A. Sloane_