cp's OEIS Frontend

A214652 a(n) = (a(n-1) + a(n-4))/gcd(a(n-1), a(n-4)) with a(1) = a(2) = a(3) = a(4) = 1.

%I A214652 #13 Jun 02 2025 08:05:24
%S A214652 1,1,1,1,2,3,4,5,7,10,7,12,19,29,36,4,23,52,22,13,36,22,2,15,17,39,41,
%T A214652 56,73,112,153,209,282,197,350,559,841,1038,694,1253,2094,522,608,
%U A214652 1861,3955,4477,5085,6946,10901,1398,2161,9107,20008,10703,12864,21971
%N A214652 a(n) = (a(n-1) + a(n-4))/gcd(a(n-1), a(n-4)) with a(1) = a(2) = a(3) = a(4) = 1.
%C A214652 A variation on A214551 with the first and fourth terms being added and divided by the greatest common divisor of the pair of numbers.
%H A214652 Reed Kelly, <a href="/A214652/b214652.txt">Table of n, a(n) for n = 1..1004</a>
%e A214652 a(11) = (a(10)+a(7))/gcd(a(10),a(7)) = (10+4)/gcd(10,4) = 7
%e A214652 a(13) = (a(12)+a(9))/gcd(a(13),a(9)) = (12+7)/gcd(12,7) = 19
%t A214652 GCDxy[n_, x_, y_, init_] := Module[{t, a, i}, t = init;
%t A214652   Do[AppendTo[t, (t[[-x]] + t[[-y]])/GCD[t[[-x]], t[[-y]]]], {n}];
%t A214652   t]; GCDxy[100, 1, 4, {1, 1, 1, 1}]
%t A214652 RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==1,a[n]==(a[n-1]+a[n-4])/GCD[ a[n-1],a[n-4]]},a,{n,60}] (* _Harvey P. Dale_, Apr 08 2019 *)
%Y A214652 cf. A003269, A214551
%K A214652 nonn
%O A214652 1,5
%A A214652 _Reed Kelly_, Jul 24 2012
%E A214652 Definition corrected by _Harvey P. Dale_, Apr 08 2019
%E A214652 NAME adapted to offset and b-file. - _R. J. Mathar_, Jun 19 2021