|
|
A280294
|
|
a(n) = a(n-1) + 2^n * a(n-2) with a(0) = 1 and a(1) = 1.
|
|
3
|
|
|
1, 1, 5, 13, 93, 509, 6461, 71613, 1725629, 38391485, 1805435581, 80431196861, 7475495336637, 666367860021949, 123144883455482557, 21958686920654707389, 8092381769059159562941, 2886261393833112966453949, 2124255587862077437434059453
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
COMMENTS
|
The Rogers-Ramanujan continued fraction is defined by R(q) = q^(1/5)/(1+q/(1+q^2/(1+q^3/(1+ ... )))). The limit of a(n)/A015459(n+2) is 2^(-1/5) * R(2).
|
|
LINKS
|
|
|
EXAMPLE
|
1/(1+2/(1+2^2/1)) = 5/7 = a(2)/A015459(4).
1/(1+2/(1+2^2/(1+2^3/1))) = 13/31 = a(3)/A015459(5).
|
|
MATHEMATICA
|
nxt[{n_, a_, b_}]:={n+1, b, b+2^(n+1)*a}; NestList[nxt, {1, 1, 1}, 20][[All, 2]] (* Harvey P. Dale, Jul 17 2020 *)
|
|
PROG
|
(Python)
def a():
a, b, p = 1, 0, 1
while True:
p, a, b = p + p, b, b + p * a
yield b
|
|
CROSSREFS
|
Cf. similar sequences with the recurrence a(n-1) + q^n * a(n-2) for n>1, a(0)=1 and a(1)=1: this sequence (q=2), A279543 (q=3), A280340 (q=10).
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|