LINKS
Yifan Xie, <a href="/A363198/b363198_1.txt">Table of n, a(n) for n = 1..2000</a>
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Revision History for A363198
(Bold, blue-underlined text is an addition; faded, red-underlined text is aShowing entries 1-10 | older changes
a(n) = n for n <= 3; for n >= 4, a(n) is the smallest positive integer that has not appeared previously in this sequence and shares a factor with a(n-1) + a(n-2) + a(n-3).
(history; published version)
(history; published version)
STATUS
proposed
approved
STATUS
editing
proposed
MATHEMATICA
Table[a[in], {i, n, 1, 65}] (* Robert P. P. McKone, Dec 30 2023 *)
PROG
(Python)
from math import gcd
a = [1, 2, 3]
t = set(a)
def next_element():
s = a[-1] + a[-2] + a[-3]
n = 1
while n in t or gcd(s, n) == 1:
n += 1
return n
def a_seq(ul):
for _ in range(4, ul + 1):
nn = next_element()
a.append(nn)
t.add(nn)
return a
print(a_seq(65)) # Robert P. P. McKone, Dec 30 2023
MATHEMATICA
a[1] = 1; a[2] = 2; a[3] = 3; a[n_] := a[n] = Module[{s, i = 1}, s = a[n - 1] + a[n - 2] + a[n - 3]; While[MemberQ[a /@ Range[1, n - 1], i] || GCD[s, i] == 1, i++]; i];
Table[a[i], {i, 1, 65}] (* Robert P. P. McKone, Dec 30 2023 *)
STATUS
proposed
editing
STATUS
editing
proposed
LINKS
Yifan Xie, <a href="/A363198/b363198_1.txt">Table of n, a(n) for n = 1..2000</a>
STATUS
approved
editing
STATUS
reviewed
approved
STATUS
proposed
reviewed
STATUS
editing
proposed