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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
1
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, 56, 73, 112, 153, 209, 282, 197, 350, 559, 841, 1038, 694, 1253, 2094, 522, 608, 1861, 3955, 4477, 5085, 6946, 10901, 1398, 2161, 9107, 20008, 10703, 12864, 21971
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.
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