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 A322780 #13 Jul 09 2025 04:48:23 %S A322780 1,4,9,32,71,252,559,1984,4401,15620,34649,122976,272791,968188, %T A322780 2147679,7622528,16908641,60012036,133121449,472473760,1048062951, %U A322780 3719778044,8251382159,29285750592,64962994321,230566226692,511452572409,1815244062944 %N A322780 First differences of A237262. %H A322780 Colin Barker, <a href="/A322780/b322780.txt">Table of n, a(n) for n = 1..1000</a> %H A322780 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,8,0,-1). %F A322780 From _Colin Barker_, Jan 06 2019: (Start) %F A322780 G.f.: x*(1 + 4*x + x^2) / (1 - 8*x^2 + x^4). %F A322780 a(n) = 8*a(n-2) - a(n-4) for n>4. %F A322780 (End) %o A322780 (PARI) Vec(x*(1 + 4*x + x^2) / (1 - 8*x^2 + x^4) + O(x^40)) \\ _Colin Barker_, Jan 06 2019 %Y A322780 Cf. A237262, A199336. %K A322780 nonn,easy %O A322780 1,2 %A A322780 _N. J. A. Sloane_, Jan 05 2019, following a suggestion from _Stan Wagon_