A373497 - OEIS

A373497

If n is prime, a(n) = 1 if the number of steps in its prime index chain is odd, a(n) = -1 if the number of steps is even, and a(n) = 0 is n is composite or 1.

0, 1, -1, 0, 1, 0, 1, 0, 0, 0, -1, 0, 1, 0, 0, 0, -1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, -1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 1, 0

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..90.

FORMULA

a(n) = 1 iff n is in A333242.

a(n) = -1 iff n is in A262275.

a(n) = 0 iff n is in A018252.

PROG

(PARI) b(n)={my(k=0); while(isprime(n), k++; n=primepi(n)); k}; \\ A078442

a(n) = if ((n==1) || !isprime(n), return(0)); if (b(n)%2, 1, -1); \\ Michel Marcus, Jun 11 2024