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A214634
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a(1) = 7; a(n) is smallest prime of the form k*a(n-1) + 3, k>0.
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1
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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
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(2) = 17 = 2 * 7 + 3.
a(3) = 37 = 2 * 17 + 3.
a(4) = 151 = 4 * 37 + 3.
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MAPLE
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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:
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MATHEMATICA
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spf[n_]:=Module[{k=1}, While[!PrimeQ[k*n+3], k++]; k*n+3]; NestList[spf, 7, 25] (* Harvey P. Dale, Aug 02 2017 *)
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PROG
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(PARI) a=7; for(n=1, 200, b=a*n+3; if(isprime(b), a=b; print1(a, ", "); next(n=1)))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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