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%I #18 Feb 10 2019 17:57:10
%S 2,2,2,2,3,3,3,3,3,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,7,7,7,7,7,7,7,7,7,
%T 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,11,11,11,11,11,11,11,11,11,11,11,11,11,
%U 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11
%N Smallest prime number greater than or equal to the square root of n.
%C Or repeat prime(k) (prime(k)^2-prime(k-1)^2) times, with prime(0) set to 0 for k=1.
%H Jean-Christophe Hervé, <a href="/A230775/b230775.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A000040(A230774(n)).
%F Repeat prime(1) prime(1)^2 times; for k>1, repeat A000040(k) A050216(k-1) times (that is, repeat prime(k) (prime(k)^2 - prime(k-1)^2) times).
%e a(5)=a(6)=a(7)=a(8)=a(9)=3 because prime(1)= 2 < sqrt(5 to 9) <= prime(2) = 3.
%t spn[n_]:=Module[{s=Sqrt[n]},If[PrimeQ[s],s,NextPrime[s]]]; Array[spn,90] (* _Harvey P. Dale_, Feb 10 2019 *)
%Y Cf. A230774, A050216, A056813.
%K nonn,easy
%O 1,1
%A _Jean-Christophe Hervé_, Nov 01 2013
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