A378550 a(n) = 1 if sigma(n) >= 2*n-1, otherwise 0.

1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for characteristic functions

Index entries for sequences related to sigma(n)

Formula

a(n) = [A000203(n) >= 2*n-1], where [ ] is the Iverson bracket.

For n > 1, a(n) = [A120444(n-1) <= 0].

a(n) = A209229(n) + A294936(n). [Conjectured]

Mathematica

Table[Boole[DivisorSigma[1, n] >= 2*n - 1], {n, 100}] (* Paolo Xausa, Dec 02 2024 *)

Prog

(PARI) A378550(n) = (sigma(n) >= 2*n-1);

Crossrefs

Characteristic function of A103288.

Cf. A000203, A120444, A209229, A294936.

Sequence in context: A341629 A365429 A322860 * A353766 A178225 A373990

Adjacent sequences: A378547 A378548 A378549 * A378551 A378552 A378553

Keyword

nonn

Author

Antti Karttunen, Dec 01 2024

Status

approved