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A354035
a(n) = 1 if n is odd and sigma(n^2) == 3 (mod 4), otherwise 0.
2
0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1
OFFSET
1
FORMULA
a(n) = A000035(n) * A000035(A083025(n)).
a(n) = A000035(n) * [A010873(A065764(n)) == 3], where [ ] is the Iverson bracket.
a(n) = A000035(n) - A354036(n).
MATHEMATICA
a[n_] := If[OddQ[n] && Mod[DivisorSigma[1, n^2], 4] == 3, 1, 0]; Array[a, 100] (* Amiram Eldar, May 16 2022 *)
PROG
(PARI) A354035(n) = ((n%2)&&3==(sigma(n*n)%4));
CROSSREFS
Characteristic function of A324909.
Sequence in context: A358678 A359150 A354031 * A025457 A350289 A219463
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 16 2022
STATUS
approved