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A031368 Odd-indexed primes: a(n) = prime(2n-1).

%I A031368 #51 Sep 08 2022 08:44:50
%S A031368 2,5,11,17,23,31,41,47,59,67,73,83,97,103,109,127,137,149,157,167,179,
%T A031368 191,197,211,227,233,241,257,269,277,283,307,313,331,347,353,367,379,
%U A031368 389,401,419,431,439,449,461,467,487,499,509,523,547,563
%N A031368 Odd-indexed primes: a(n) = prime(2n-1).
%C A031368 Appeared as a puzzle in "Stickelers", a nationally distributed feature, by Terry Stickels, Sep 28 2006. - _Franklin T. Adams-Watters_, Sep 28 2006
%C A031368 Also every second prime starting with 2. - _Cino Hilliard_, Dec 02 2007
%C A031368 Central terms of the triangle in A005145. - _Reinhard Zumkeller_, Aug 05 2009
%H A031368 Reinhard Zumkeller, <a href="/A031368/b031368.txt">Table of n, a(n) for n = 1..10000</a>
%F A031368 a(n) = A219603(n) / A000040(n). - _Reinhard Zumkeller_, Nov 25 2012
%p A031368 A031368 := n->ithprime(2*n-1): seq(A031368(n), n=1..100);
%t A031368 Table[ Prime[ 2n -1], {n, 52}] (* _Robert G. Wilson v_, Dec 01 2013 *)
%o A031368 (Magma) [ NthPrime(2*n-1): n in [1..1000] ]; // _Vincenzo Librandi_, Apr 11 2011
%o A031368 (Haskell)
%o A031368 a031368 = a000040 . ((subtract 1) . (* 2))
%o A031368 a031368_list = map a000040 [1, 3 ..]  -- _Reinhard Zumkeller_, Nov 25 2012
%o A031368 (PARI) a(n) = prime(2*n-1) \\ _Jianing Song_, Jun 03 2021
%Y A031368 Cf. A000040, A031215 (even-indexed primes), A005408.
%Y A031368 First differences are A155067.
%K A031368 nonn,easy
%O A031368 1,1
%A A031368 _Jeff Burch_