A191112 First occurrence of the n-th odd prime in A190911.
1, 3, 12, 42, 165, 3000, 2142, 39270, 838695, 2185092, 194467182, 649154415, 33547795512, 40753286805, 24563658547425, 1364238471026340, 2297427262231332, 1662166966658270160, 783186317937632697, 404695317060455732220, 162293533192142440777455, 634357227813958501290435
Offset: 1
Keywords
Crossrefs
Cf. A190911.
Programs
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Maple
A190911 := proc(n) option remember: local k: for k from 3 by 2 do if(gcd(k,n)=1 and gcd(k,n+3)=1)then return k: fi: od: end: for n from 2 do p:=ithprime(n): for k from 1 do if(A190911(k)=p)then print(k): break: fi: od: od:
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PARI
A190911(n)=n*=n+3;forprime(p=3,,if(n%p,return(p))) {my(v=[0],t=3,p=5); print1("1, 3"); forprime(q=7,1000, u=vector(#v); for(i=1,#u, u[i]=lift(chinese(Mod(v[i],t),Mod( 0,p))); v[i]=lift(chinese(Mod(v[i],t),Mod(-3,p))) ); v=vecsort(concat(u,v)); for(j=2,#v, if(A190911(v[j])==q, print1(", "v[j]); break ) ); t*=p; p=q )} \\ Charles R Greathouse IV, Oct 09 2011
Formula
a(n) = 0 (mod 3) for n >= 2.
a(n) = 0 or 12 (mod 15) for n >= 3.
Extensions
a(11)-a(22) from Charles R Greathouse IV, Oct 09 2011