A203018 - OEIS

%I #8 Oct 30 2018 10:31:02

%S 5,41,61,193,241,337,449,673,613,1201,1453,1249,2081,2633,1861,3457,

%T 4217,3169,6841,4801,4201,7481,9109,6529,7901,13001,8209,12097,12413,

%U 8641,16741,17921,10429,19993,15401,16417,24421,26297,17317,23201,33457,21169

%N The n-th prime number that equals 1 (mod 4n).

%H Zak Seidov, <a href="/A203018/b203018.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1)=5 because 1+4=5 is 1st prime == 1 mod 4,

%e a(2)=41 because 1+(4*2)*{2,5}={17,41} are 1st and 2nd primes == 1 mod 8,

%e a(3)=61 because 1+(4*3)*{1,3,5}={13,37,61} are 1st, 2nd and 3rd primes == 1 mod 12;

%e a(1000)=24952001=1+4000*6238;

%e a(10000)=3345120001=1+40000*83628;

%e a(10^5)=411686400001=A000040(16018223727)=1+4*10^6*1029216;

%e a(10^6)=48792928000001=A000040(1600641618847)=1+4*10^6*12198232.

%Y Cf. A000040, A002144, A070848.

%K nonn

%O 1,1

%A _Zak Seidov_, Dec 27 2011