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A048388 Replacing digits d in decimal expansion of n with d^2 yields a prime. 4

%I #17 Oct 14 2019 05:04:28

%S 11,13,17,19,21,27,51,57,71,73,81,87,89,91,101,103,107,119,123,129,

%T 131,133,137,149,153,161,167,169,173,189,191,197,199,201,203,207,213,

%U 223,229,231,233,249,253,267,283,307,311,313,319,321,331,337,341,359,371

%N Replacing digits d in decimal expansion of n with d^2 yields a prime.

%H Harvey P. Dale, <a href="/A048388/b048388.txt">Table of n, a(n) for n = 1..1001</a> [offset shifted by _Georg Fischer_, Oct 14 2019]

%e 199 = (1)(9)(9) -> (1)(81)(81) = 18181 which is a prime.

%t Select[Range[400],PrimeQ[FromDigits[Flatten[IntegerDigits/@ (IntegerDigits[ #]^2)]]]&] (* _Harvey P. Dale_, Oct 13 2013 *)

%Y Cf. A048385, A048389.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Mar 15 1999

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)