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 A049296 #24 Apr 06 2014 08:13:30
%S A049296 10,2,4,2,4,6,2,6,4,2,4,6,6,2,6,4,2,6,4,6,8,4,2,4,2,4,8,6,4,6,2,4,6,2,
%T A049296 6,6,4,2,4,6,2,6,4,2,4,2,10,2,10,2,4,2,4,6,2,6,4,2,4,6,6,2,6,4,2,6,4,
%U A049296 6,8,4,2,4,2,4,8,6,4,6,2,4,6,2,6,6,4,2,4,6,2,6,4,2,4,2,10,2,10,2,4,2,4,6,2
%N A049296 First differences of A008364. Also first differences of reduced residue system (RRS) for 4th primorial number, A002110(4)=210.
%C A049296 First differences of reduced residue systems modulo primorial numbers are essentially palindromic + 1 separator term (2). The palindromic part starts and ends with p_(n+1)-1 for the n-th primorial number.
%C A049296 This sequence has period A005867(4)=A000010(A002110(4))=48. The 0th, first, 2nd and 3rd similar difference sequences are as follows: {1},{2},{4,2},{6,4,2,4,2,4,6,2} obtained from reduced residue systems of consecutive primorials.
%C A049296 Difference sequence of the "4th diatomic sequence" - A. de Polignac (1849), J. Dechamps (1907).
%D A049296 Dickson L. E., History of the Theory of Numbers, Vol. 1, p. 439, Chelsea, 1952.
%H A049296 Reinhard Zumkeller, <a href="/A049296/b049296.txt">Table of n, a(n) for n = 1..1000</a>
%t A049296 t1=Table[ GCD[ w, 210 ], {w, 1, 210} ] /t2=Flatten[ Position[ t1, 1 ] ] /t3=Mod[ RotateLeft[ t2 ]-t2, 210 ]
%t A049296 Differences[Select[Range[600],GCD[#,210]==1&]] (* _Harvey P. Dale_, Jan 13 2012 *)
%o A049296 (Haskell)
%o A049296 a049296 n = a049296_list !! (n-1)
%o A049296 a049296_list = zipWith (-) (tail a008364_list) a008364_list
%o A049296 -- _Reinhard Zumkeller_, Jan 06 2013
%Y A049296 Cf. A005867, A008364, A002110, A001223.
%K A049296 nonn,easy,nice
%O A049296 1,1
%A A049296 _Labos Elemer_
%E A049296 Corrected by Frederic Devaux, Feb 02 2007