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, 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.

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

cf. A003269, A214551

Sequence in context: A302940 A272072 A118463 * A137929 A094617 A254318

Adjacent sequences: A214649 A214650 A214651 * A214653 A214654 A214655

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