This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A138420 #18 Aug 01 2025 15:31:08
%S A138420 3,18,150,588,3630,7098,20808,32490,69828,176610,230640,468198,706020,
%T A138420 854238,1219368,1971918,3028470,3460530,5036658,6351660,7098228,
%U A138420 9735960,11862858,15683580,22129968,26012550,28135068,32767038,35286570
%N A138420 a(n) = ((prime(n))^4-(prime(n))^2)/4.
%C A138420 Number of monic irreducible polynomials of degree 4 over GF(prime(n)). - _Robert Israel_, Jan 07 2015
%H A138420 Vincenzo Librandi, <a href="/A138420/b138420.txt">Table of n, a(n) for n = 1..200</a>
%F A138420 a(n) = A138402(n)/4. - _R. J. Mathar_, Oct 15 2017
%p A138420 seq(1/4*(ithprime(i)^4 - ithprime(i)^2), i=1..100); # _Robert Israel_, Jan 07 2015
%t A138420 a = {}; Do[p = Prime[n]; AppendTo[a, (p^4 - p^2)/4], {n, 1, 50}]; a
%t A138420 (#^4-#^2)/4&/@Prime[Range[30]] (* _Harvey P. Dale_, Aug 01 2025 *)
%o A138420 (Magma) [(NthPrime((n))^4 - NthPrime((n))^2)/4: n in [1..30] ]; // _Vincenzo Librandi_, Jun 17 2011
%o A138420 (PARI) forprime(p=2,1e3,print1((p^4-p^2)/4", ")) \\ _Charles R Greathouse IV_, Jul 15 2011
%Y A138420 Cf. A008837, A127919, A138420, A138426.
%K A138420 nonn,easy
%O A138420 1,1
%A A138420 _Artur Jasinski_, Mar 19 2008
%E A138420 Name edited by _Robert Israel_, Jan 07 2015