A077149 a(1) =3. For n>1, a(n) = smallest k such that there are n numbers m not relatively prime to n in range n < m < k.

3, 7, 13, 13, 31, 16, 57, 25, 37, 27, 133, 31, 183, 39, 49, 49, 307, 46, 381, 55, 71, 63, 553, 61, 151, 75, 109, 78, 871, 71, 993, 97, 118, 99, 148, 91, 1407, 111, 142, 107, 1723, 101, 1893, 125, 142, 135, 2257, 121, 393, 135, 188, 149, 2863, 136, 256, 155

Offset

1,1

Comments

a(p) = p^2 + p +1, a(2^m) = 3*2^m +1,a(p^m) = p^m + p^(m+1) +1, if p is a prime.

Links

Table of n, a(n) for n=1..56.

Example

a(5) = 31 as there are 5 non-coprime numbers to 5 between 5 and 31, i.e. 10,15,20,25 and 30.

Prog

(PARI) print1("3, "):for(n=2, 100, s=0:for(k=n+1, 10^9, if(gcd(n, k)>1, s=s+1): if(s==n, s=k:break)):print1(s+1", "))

Crossrefs

Cf. A077148.

Sequence in context: A108768 A238476 A118889 * A290642 A295009 A310251

Adjacent sequences: A077146 A077147 A077148 * A077150 A077151 A077152

Keyword

nonn

Author

Amarnath Murthy, Oct 30 2002

Extensions

More terms from Ralf Stephan, Mar 25 2003

Status

approved