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

Author

Antti Karttunen, Jul 28 2022

Keywords

• nonn

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

Crossrefs

Odd terms in A319630.

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

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

Programs

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);