A349165 Numbers k such that sigma(k) and A003961(k) are relatively prime, where A003961(n) is fully multiplicative function with a(prime(k)) = prime(k+1).

1, 3, 4, 5, 7, 9, 11, 12, 13, 15, 16, 17, 19, 21, 23, 25, 28, 29, 31, 33, 35, 36, 37, 39, 41, 43, 45, 47, 48, 49, 51, 52, 53, 55, 59, 61, 63, 64, 67, 69, 71, 73, 75, 76, 77, 79, 81, 83, 84, 85, 89, 91, 93, 95, 97, 101, 103, 105, 107, 109, 111, 112, 113, 115, 117, 119, 121, 123, 124, 125, 127, 129, 131, 133, 137, 139

Offset

1,2

Links

Table of n, a(n) for n=1..76.

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); };
isA349165(n) = (1==gcd(sigma(n), A003961(n)));

Crossrefs

Cf. A000203, A003961.

Positions of ones in A342671, and also in A349163.

Cf. A349166 (complement), A349167 (characteristic function).

Sequence in context: A361924 A187691 A141259 * A047501 A256455 A035242

Adjacent sequences: A349162 A349163 A349164 * A349166 A349167 A349168

Keyword

nonn

Author

Antti Karttunen, Nov 09 2021

Status

approved