A379478 a(n) = 1 if the greatest common divisor of n, sigma(n) and A003961(n) is 1 and gcd(A003961(n)-2n, A003961(n)-sigma(n)) > 1, otherwise 0.

0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 1, 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, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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 prime indices in the factorization of n.

Index entries for sequences related to sigma(n).

Formula

a(n) = A379476(n) - A379475(n).

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A372565(n) = gcd([n, sigma(n), A003961(n)]);
A326057(n) = { my(u=A003961(n)); gcd(u-(2*n), u-sigma(n)); };
A379478(n) = ((1==A372565(n)) && (A326057(n)>1));

Crossrefs

Characteristic function of A379479.

Cf. A000203, A003961, A326057, A372565, A379475, A379476.

Sequence in context: A079365 A037822 A144600 * A011686 A275305 A169671

Adjacent sequences: A379475 A379476 A379477 * A379479 A379480 A379481

Keyword

nonn

Author

Antti Karttunen, Dec 23 2024

Status

approved