|
|
A069228
|
|
a(1)=1, a(2)=4, a(n+2)=(a(n+1)+a(n))/b(n), where b(n)=gcd(a(n+1)+a(n),4).
|
|
1
|
|
|
1, 4, 5, 9, 7, 4, 11, 15, 13, 7, 5, 3, 2, 5, 7, 3, 5, 2, 7, 9, 4, 13, 17, 15, 8, 23, 31, 27, 29, 14, 43, 57, 25, 41, 33, 37, 35, 18, 53, 71, 31, 51, 41, 23, 16, 39, 55, 47, 51, 49, 25, 37, 31, 17, 12, 29, 41, 35, 19, 27, 23, 25, 12, 37, 49, 43, 23, 33, 14, 47, 61, 27, 22, 49, 71
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
A Collatz-Fibonacci mixture. Conjecture : sequence diverges to infinity.
|
|
LINKS
|
|
|
EXAMPLE
|
a(4)=9 a(5)=7 so gcd(a(4)+a(5),4)=4 and hence a(6)=16/4=4.
|
|
MAPLE
|
f:= proc(n) option remember;
(procname(n-1)+procname(n-2))/igcd(procname(n-1)+procname(n-2), 4)
end proc:
f(1):= 1: f(2):= 4:
|
|
MATHEMATICA
|
a[n_] := a[n] = Switch[n, 1, 1, 2, 4, _, (a[n-1] + a[n-2])/GCD[a[n-1] + a[n-2], 4]];
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|