A377984 a(n) = 2*sigma(n) - A003961(n), where sigma is the sum of divisors function and A003961 is fully multiplicative function with a(prime(i)) = prime(i+1).

1, 3, 3, 5, 5, 9, 5, 3, 1, 15, 11, 11, 11, 15, 13, -19, 17, 3, 17, 21, 9, 33, 19, -15, 13, 33, -45, 13, 29, 39, 27, -117, 31, 51, 19, -43, 35, 51, 27, -9, 41, 27, 41, 51, -19, 57, 43, -157, -7, 39, 49, 43, 49, -135, 53, -57, 45, 87, 59, 21, 57, 81, -67, -475, 49, 93, 65, 81, 47, 57, 71, -285, 69, 105, 3, 73, 49, 81

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A377984(n) = (2*sigma(n) - A003961(n));

Crossrefs

Cf. A000203, A003961.

Cf. A337378 (positions of negative terms), A337379 (of positive terms), A337380 (their characteristic function), A377985 (Möbius transform).

Sequence in context: A026924 A240313 A275369 * A062130 A151970 A049644

Adjacent sequences: A377981 A377982 A377983 * A377985 A377986 A377987

Keyword

sign

Author

Antti Karttunen, Nov 16 2024

Status

approved