OFFSET
1,5
COMMENTS
All terms are perfect squares.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..15
FORMULA
a(n) = A072878(n)^2.
a(n) = 16*a(n-1)*a(n-2)*a(n-3) - 2a(n-1) - 2a(n-2) - 2a(n-3) - a(n-4).
a(n)*a(n-1)*a(n-2)*a(n-3) = ((a(n) + a(n-1) + a(n-2) + a(n-3))/4)^2.
MATHEMATICA
RecurrenceTable[{a[n] == (a[n - 1] + a[n - 2] + a[n - 3])^2/a[n - 4], a[1] == a[2] == a[3] == a[4] == 1}, a, {n, 1, 12}] (* Michael De Vlieger, Aug 18 2016 *)
nxt[{a_, b_, c_, d_}]:={b, c, d, (b+c+d)^2/a}; NestList[nxt, {1, 1, 1, 1}, 10][[;; , 1]] (* Harvey P. Dale, Aug 20 2024 *)
PROG
(Ruby)
def A(m, n)
a = Array.new(m, 1)
ary = [1]
while ary.size < n
i = a[1..-1].inject(:+)
j = i * i
break if j % a[0] > 0
a = *a[1..-1], j / a[0]
ary << a[0]
end
ary
end
def A276095(n)
A(4, n)
end
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 18 2016
STATUS
approved