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 A185017 #20 Jun 18 2024 12:00:28 %S A185017 0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %T A185017 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A185017 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A185017 Characteristic function of 7. %C A185017 Number of connected 2-regular (simple) graphs with girth exactly 7. %C A185017 The Euler transformation of this sequence is A082784. %H A185017 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1). %F A185017 a(n) = A185117(n) - A185118(n). %o A185017 (Python) %o A185017 def A185017(n): return int(n==7) # _Chai Wah Wu_, Feb 04 2022 %Y A185017 Characteristic function of g: A000007 (g=0), A063524 (g=1), A185012 (g=2), A185013 (g=3), A185014 (g=4), A185015 (g=5), A185016 (g=6), this sequence (g=7). %Y A185017 Cf. A185117, A185118. %K A185017 nonn,easy %O A185017 0,1 %A A185017 _Jason Kimberley_, Oct 14 2011