A356171 Odd numbers that are not divisible by two consecutive prime numbers.

1, 3, 5, 7, 9, 11, 13, 17, 19, 21, 23, 25, 27, 29, 31, 33, 37, 39, 41, 43, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 137, 139, 141, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163

Offset

1,2

Comments

Numbers k such that k and the smallest positive x such that k divides x*A003961(x) are coprime, where A003961 is fully multiplicative with a(p) = nextprime(p).

Links

Antti Karttunen, Table of n, a(n) for n = 1..28906; terms up to 65537

Index entries for sequences computed from indices in prime factorization

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A356172(n) = for(k=1, oo, if((k*A003961(k))%n==0, return(1==gcd(n, k))));
isA356171(n) = A356172(n);

Crossrefs

Odd terms in A319630.

Positions of 1's in A356166, positions of 0's in A356169.

Cf. A003961, A356164, A356172 (characteristic function).

Sequence in context: A324846 A324760 A324761 * A244579 A151991 A360114

Adjacent sequences: A356168 A356169 A356170 * A356172 A356173 A356174

Keyword

nonn

Author

Antti Karttunen, Jul 28 2022

Status

approved