OFFSET
1,5
COMMENTS
A variation on A214551 with the first and fourth terms being added and divided by the greatest common divisor of the pair of numbers.
LINKS
Reed Kelly, Table of n, a(n) for n = 1..1004
EXAMPLE
a(11) = (a(10)+a(7))/gcd(a(10),a(7)) = (10+4)/gcd(10,4) = 7
a(13) = (a(12)+a(9))/gcd(a(13),a(9)) = (12+7)/gcd(12,7) = 19
MATHEMATICA
GCDxy[n_, x_, y_, init_] := Module[{t, a, i}, t = init;
Do[AppendTo[t, (t[[-x]] + t[[-y]])/GCD[t[[-x]], t[[-y]]]], {n}];
t]; GCDxy[100, 1, 4, {1, 1, 1, 1}]
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 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reed Kelly, Jul 24 2012
EXTENSIONS
Definition corrected by Harvey P. Dale, Apr 08 2019
NAME adapted to offset and b-file. - R. J. Mathar, Jun 19 2021
STATUS
approved