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A367131
a(n) is the sum of the divisors of A000058(n) (Sylvester's sequence).
2
3, 4, 8, 44, 1960, 3263444, 10697794573312, 113429214231136770625234912, 12864938683281101589385656009398714729057117020127552, 166504803622354833425112235578181474001920862856209391632362182416351065666575351284563698791731209336320
OFFSET
0,1
FORMULA
a(n) = sigma(A000058(n)) = A000203(A000058(n)).
MATHEMATICA
a000058[0] = 2; a000058[n_Integer?NonNegative] := a000058[n] = a000058[n - 1]^2 - a000058[n - 1] + 1; a[n_Integer?NonNegative] := a[n] = DivisorSigma[1, a000058[n]]; Table[a[n], {n, 0, 9}] (* Robert P. P. McKone, Nov 05 2023 *)
PROG
(Python)
from sympy import divisor_sigma
memo = {0: 2}
def a000058(n):
if n not in memo:
memo[n] = a000058(n - 1)**2 - a000058(n - 1) + 1
return memo[n]
a = lambda n: divisor_sigma(a000058(n))
print([a(n) for n in range(10)])
# Robert P. P. McKone, Nov 05 2023
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Sean A. Irvine, Nov 05 2023
STATUS
approved