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a(n)=prevprime[A090116(n)], the largest prime previous to squares given in A090116, being such that distance of a(n) to the following prime equals 2n.
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%I #6 Oct 15 2013 22:32:21

%S 3,7,23,359,139,619,113,1933,523,887,3229,1669,2477,10399,5749,10799,

%T 9973,22193,30593,25261,121081,76163,93001,157579,212507,35677,118973,

%U 1121453,190921,672379,693881,1003963,259033,1646033,675643,1207769

%N a(n)=prevprime[A090116(n)], the largest prime previous to squares given in A090116, being such that distance of a(n) to the following prime equals 2n.

%F a(n)=prevprime[A090116(n)^2]-prevprime[A090117(n)]=p[pi[A090117(n)]]

%e n=7: a(7)=113 because 127-113=14=2.7 and 121=11 is

%e between {127,113} closest primes; also 113 is

%e the smallest prime with this property.

%t pre[x_ := Prime[PrimePi[x]] nex[x_ := Prime[PrimePi[x]+1] de[x_ := Prime[PrimePi[x]+1]-Prime[PrimePi[x]] t=Table[de[w^2], {w, 1, 50000}]; mt=Table[Min[Flatten[Position[t, 2*j]]], {j, 1, 100}] Table[pre[Part[mt, j]^2], {j, 1, Length[mt]}]

%Y Cf. A090116-A090119.

%K nonn

%O 1,1

%A _Labos Elemer_, Jan 09 2004