OFFSET
1,5
COMMENTS
Partial sums of the odd-indexed terms of Chowla's function A048050.
a(n) has a symmetric representation.
MAPLE
a:= proc(n) option remember; `if`(n=1, 0,
a(n-1)+numtheory[sigma](2*n-1)-2*n)
end:
seq(a(n), n=1..60); # Alois P. Heinz, Aug 19 2021
MATHEMATICA
s[1] = 0; s[n_] := DivisorSigma[1, 2*n - 1] - 2*n; Accumulate @ Array[s, 50] (* Amiram Eldar, Aug 19 2021 *)
Accumulate[Join[{0}, Table[DivisorSigma[1, n]-n-1, {n, 3, 151, 2}]]] (* Harvey P. Dale, Jul 29 2023 *)
PROG
(Python)
from sympy import divisors
from itertools import accumulate
def A346879(n): return sum(divisors(2*n-1)[1:-1])
def aupton(nn): return list(accumulate(A346879(n) for n in range(1, nn+1)))
print(aupton(60)) # Michael S. Branicky, Aug 19 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Aug 18 2021
STATUS
approved