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A167722 Squares that become prime numbers when prefixed with a 7. 1

%I #14 Jun 22 2016 08:29:28

%S 1,9,121,529,841,1089,1849,3721,4489,4761,5041,5329,6561,7569,8649,

%T 9801,10609,12321,17161,23409,28561,32041,32761,33489,39601,45369,

%U 49729,51529,54289,61009,62001,63001,66049,69169,71289,76729,88209,94249

%N Squares that become prime numbers when prefixed with a 7.

%C For obvious reasons, all terms are odd. - _Harvey P. Dale_, Sep 30 2012

%C Subsequence of squares of A032670. - _Michel Marcus_, Jun 22 2016

%H G. C. Greubel, <a href="/A167722/b167722.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[1,400,2]^2,PrimeQ[FromDigits[Join[{7},IntegerDigits[#]]]]&] (* _Harvey P. Dale_, Sep 30 2012 *)

%Y Cf. A032670.

%K base,nonn

%O 1,2

%A _Claudio Meller_, Nov 10 2009

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Last modified March 28 22:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)