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Squares that become prime numbers when prefixed with an 8.
1

%I #10 Nov 28 2016 02:42:38

%S 9,81,2601,3969,4761,6561,25281,31329,35721,56169,59049,68121,71289,

%T 91809,131769,149769,168921,194481,199809,210681,221841,263169,301401,

%U 335241,370881,423801,439569,463761,480249,576081,603729,613089,622521

%N Squares that become prime numbers when prefixed with an 8.

%C Subsequence of squares of A032671. - _Michel Marcus_, Jun 22 2016

%H G. C. Greubel, <a href="/A167723/b167723.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[1, 500000, 2]^2, PrimeQ[FromDigits[Join[{8}, IntegerDigits[#]]]] &] (* _G. C. Greubel_, Jun 21 2016 *)

%Y Cf. A032671.

%K base,nonn

%O 1,1

%A _Claudio Meller_, Nov 10 2009