reviewed
approved
proposed
editing
Cf. A225402, A225404, A309600.
(Ruby)
def A225407(n)
ary = [3]
a = 3
n.times{|i|
b = (a + 7 * (a ** 3 + 3)) % (10 ** (i + 2))
ary << (b - a) / (10 ** (i + 1))
a = b
}
ary
end
p A225407(100) # Seiichi Manyama, Aug 13 2019
Define the sequence {b(n)} by the recurrence b(0) = 0 and b(1) = 3, b(n) = b(n-1) + 7 * (b(n-1)^3 + 3) mod 10^n for n > 1, then a(n) = (b(n+1) - b(n))/10^n. - Seiichi Manyama, Aug 13 2019
Seiichi Manyama, <a href="/A225407/b225407.txt">Table of n, a(n) for n = 0..10000</a>
