OFFSET
1,1
COMMENTS
a(n)=(A153048(n))^2.
There are exactly 15 such numbers.
MATHEMATICA
c = 0; t = 1000; re = Sort[Reap[Do[If[PrimeQ[p], Do[If[PrimeQ[q], r = p*t + q; s = Sqrt[r]; If[s == Floor[s], c++; Sow[r]]], {q, 101, 999, 2}]], {p, 101, 999, 2}]][[2, 1]]]
concatpQ[n_]:=Module[{idn=IntegerDigits[n], a, b}, a=FromDigits[Take[idn, 3]]; b=FromDigits[Take[idn, -3]]; IntegerLength[a]==IntegerLength[b]==3 && PrimeQ[a]&&PrimeQ[b]]; Select[Range[316, 1000]^2, concatpQ] (* Harvey P. Dale, Mar 09 2012 *)
CROSSREFS
KEYWORD
fini,full,nonn,base
AUTHOR
Zak Seidov, Dec 17 2008
STATUS
approved