A353478 a(n) = 1 if n is an even semiprime (2*prime), otherwise 0.

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

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Formula

If A000035(n) = 0, then a(n) = A010051(n/2), otherwise 0.

a(n) = A059841(n) * A064911(n).

a(n) = A064911(n) - A353480(n).

Mathematica

Table[If[PrimeQ[n/2], 1, 0], {n, 150}] (* Harvey P. Dale, Aug 11 2025 *)

Prog

(PARI) A353478(n) = ((0==(n%2)) && isprime(n/2));

Crossrefs

Characteristic function of A100484, the primes doubled.

Cf. A000035, A010051, A059841, A064911, A353477, A353479, A353480.

Sequence in context: A234577 A038189 A072783 * A353555 A353476 A288377

Adjacent sequences: A353475 A353476 A353477 * A353479 A353480 A353481

Keyword

nonn

Author

Antti Karttunen, Apr 22 2022

Status

approved