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 A045800 #28 Jul 09 2025 03:50:53
%S A045800 1,7,43,49,101,107,143,149,201,207,243,249,301,307,343,349,401,407,
%T A045800 443,449,501,507,543,549,601,607,643,649,701,707,743,749,801,807,843,
%U A045800 849,901,907,943,949,1001,1007,1043,1049,1101,1107,1143,1149,1201,1207
%N A045800 0-ish numbers (end in 01, 07, 43, 49).
%H A045800 Reinhard Zumkeller, <a href="/A045800/b045800.txt">Table of n, a(n) for n = 1..1000</a>
%H A045800 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1).
%F A045800 G.f.: x*(1+6*x+36*x^2+6*x^3+51*x^4)/(1-x-x^4+x^5). - _Colin Barker_, Jan 23 2012
%F A045800 a(n) = (50*n-8*i^(n*(n+1))-19*(-1)^n-75)/2, where i=sqrt(-1). - _Bruno Berselli_, Feb 22 2012
%t A045800 LinearRecurrence[{1,0,0,1,-1},{1,7,43,49,101},60] (* _Harvey P. Dale_, Jul 26 2015 *)
%o A045800 (Haskell)
%o A045800 import Data.List (findIndices)
%o A045800 a045800 n = a045800_list !! (n-1)
%o A045800 a045800_list = findIndices (`elem` [1,7,43,49]) $ cycle [0..99]
%o A045800 -- _Reinhard Zumkeller_, Jan 23 2012
%Y A045800 Cf. A045801-A045809, A045572, A045797, A045798.
%K A045800 nonn,base,easy
%O A045800 1,2
%A A045800 _J. H. Conway_
%E A045800 More terms from _Erich Friedman_.