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A076830 Least square s such that A078142(s) is equal to the n-th prime. 1

%I #14 Dec 11 2019 05:23:19

%S 4,36,121,484,2809,11236,6889,27556,29929,51529,85849,744769,196249,

%T 734449,727609,942841,1203409,4813636,1510441,1885129,7540516,8048569,

%U 4932841,4108729,7946761,12243001,18088009,10608049,12187081,10569001

%N Least square s such that A078142(s) is equal to the n-th prime.

%H Amiram Eldar, <a href="/A076830/b076830.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1) = 4 since 4 = 2^2 is the least square s such that A078142(s) = 2, the first prime.

%e a(2) = 36 since 36 = 6^2 is the least square s such that A078142(s) = 3, the second prime.

%t s[n_] := Total[Ceiling[Sqrt[(p = FactorInteger[n][[;; , 1]])]]^2 - p]; m = 30; seq = Table[0, {m}]; c = 0; k = 1; While[c < m, n = s[k^2]; If[PrimeQ[n] && (i = PrimePi[n]) <= m && seq[[i]] == 0, c++; seq[[i]] = k^2]; k++]; seq (* _Amiram Eldar_, Dec 11 2019 *)

%Y Cf. A078142.

%K nonn

%O 1,1

%A _Jason Earls_, Nov 21 2002

%E Name edited by _Amiram Eldar_, Dec 11 2019

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