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n-th Euler (secant, zig) number A000364(n) is prime.
2

%I #25 Aug 24 2020 22:44:08

%S 2,3,19,227,255

%N n-th Euler (secant, zig) number A000364(n) is prime.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EulerNumber.html">Euler Number.</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>

%t Select[Range[100], PrimeQ[EulerE[#]] &]/2 (* _Harvey P. Dale_, Aug 10 2011 *)

%Y Cf. A000364.

%K more,nonn

%O 1,1

%A _Eric W. Weisstein_

%E Offset corrected by _Arkadiusz Wesolowski_, Oct 17 2011