A214634 a(1) = 7; a(n) is smallest prime of the form k*a(n-1) + 3, k>0.

7, 17, 37, 151, 607, 1217, 2437, 4877, 39019, 78041, 624331, 6243313, 174812767, 1398502139, 19579029949, 39158059901, 1957902995053, 15663223960427, 156632239604273, 3132644792085463, 181693397940956857, 726773591763827431, 7267735917638274313, 1148302274986847341457, 4593209099947389365831

Offset: 1

Author

Robin Garcia, Jul 23 2012

Keywords

• nonn

Examples

			a(2) = 17 = 2 * 7 + 3.
a(3) = 37 = 2 * 17 + 3.
a(4) = 151 = 4 * 37 + 3.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..390

Crossrefs

Cf. A061092, A059411, A214523, A214632, A214633

Programs

Maple

A214634 := proc(n)
    option remember;
    local k;
    if n =  1 then
        7;
    else
        for k from 1 do
            if isprime(k*procname(n-1)+3) then
                return k*procname(n-1)+3 ;
            end if;
        end do:
    end if;
end proc:
seq(A214634(n),n=1..20) ; # R. J. Mathar, Jul 23 2012

Mathematica

spf[n_]:=Module[{k=1},While[!PrimeQ[k*n+3],k++];k*n+3]; NestList[spf,7,25] (* Harvey P. Dale, Aug 02 2017 *)

PARI

a=7;for(n=1,200,b=a*n+3;if(isprime(b),a=b;print1(a,", ");next(n=1)))

Extensions

More terms from Robert Israel, Nov 23 2016