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 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. 1

%I

%S 3,7,13,13,31,16,57,25,37,27,133,31,183,39,49,49,307,46,381,55,71,63,

%T 553,61,151,75,109,78,871,71,993,97,118,99,148,91,1407,111,142,107,

%U 1723,101,1893,125,142,135,2257,121,393,135,188,149,2863,136,256,155

%N 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.

%C 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.

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

%o (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","))

%Y Cf. A077148.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Oct 30 2002

%E More terms from _Ralf Stephan_, Mar 25 2003

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Last modified April 7 15:56 EDT 2020. Contains 333306 sequences. (Running on oeis4.)