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A298356 a(n) = a(n-1) + a(n-2) + a([n/2]) + a([n/3]) + ... + a([n/n]), where a(0) = 1, a(1) = 1, a(2) = 1. 2
1, 1, 1, 4, 8, 16, 32, 57, 103, 178, 308, 514, 874, 1441, 2394, 3926, 6462, 10531, 17231, 28001, 45614, 74026, 120258, 194903, 316210, 512171, 830007, 1343883, 2176578, 3523150, 5704107, 9231637, 14942711, 24181525, 39135483, 63328289, 102482212, 165828942 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
COMMENTS
a(n)/a(n-1) -> (1 + sqrt(5))/2, the golden ratio (A001622), so that (a(n)) has the growth rate of the Fibonacci numbers (A000045). See A298338 for a guide to related sequences.
LINKS
MATHEMATICA
a[0] = 1; a[1] = 1; a[2] = 1;
a[n_] := a[n] = a[n - 1] + a[n - 2] + Sum[a[Floor[n/k]], {k, 2, n}];
Table[a[n], {n, 0, 30}] (* A298356 *)
PROG
(Python)
from functools import lru_cache
@lru_cache(maxsize=None)
def A298356(n):
if n <= 2:
return 1
c, j = A298356(n-1)+A298356(n-2), 2
k1 = n//j
while k1 > 1:
j2 = n//k1 + 1
c += (j2-j)*A298356(k1)
j, k1 = j2, n//j2
return c+n-j+1 # Chai Wah Wu, Mar 31 2021
CROSSREFS
Sequence in context: A003199 A189925 A007096 * A036313 A121986 A285906
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Feb 10 2018
STATUS
approved

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Last modified March 28 07:48 EDT 2024. Contains 371235 sequences. (Running on oeis4.)