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 A381219 #15 Aug 13 2025 16:24:49
%S A381219 1,11,170,3450,87864,2715720,99248400,4200210000,202383054720,
%T A381219 10949741066880,657619863264000,43423960900320000,3127284944109849600,
%U A381219 243957907264508236800,20493712266753293568000,1844490309401727187200000,177073768932670444843008000,18061662138488384327847936000,1950666948832313303630438400000
%N A381219 a(n) = (6^n+2^n-2*3^n)*(n-1)!/2.
%C A381219 This is the sequence associated with the gamma-chain (see Broadhurst link).
%H A381219 David Broadhurst, <a href="https://vimeo.com/1054325156?share=copy">Resurgent Integer Sequences</a>, Rutgers Experimental Math Seminar, Feb 06 2025; <a href="https://sites.math.rutgers.edu/~zeilberg/expmath/broadhurst2025.pdf">Slides</a>.
%F A381219 D-finite with recurrence a(n) +11*(-n+1)*a(n-1) +36*(n-1)*(n-2)*a(n-2) -36*(n-1)*(n-2)*(n-3)*a(n-3)=0. - _R. J. Mathar_, Feb 18 2025
%t A381219 Table[(6^n+2^n-2*3^n) (n-1)!/2,{n,20}] (* _Harvey P. Dale_, Aug 13 2025 *)
%Y A381219 Cf. A379809.
%K A381219 nonn
%O A381219 1,2
%A A381219 _N. J. A. Sloane_, Feb 17 2024, based on an email from _David Broadhurst_