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 A066499 #30 Dec 11 2024 11:34:00
%S A066499 3,4,6,7,9,11,14,18,19,22,23,27,31,38,43,46,47,49,54,59,62,67,71,79,
%T A066499 81,83,86,94,98,103,107,118,121,127,131,134,139,142,151,158,162,163,
%U A066499 166,167,179,191,199,206,211,214,223,227,239,242,243,251,254,262,263,271
%N A066499 Numbers k such that phi(k) == 2 (mod 4).
%C A066499 Related to the equation x^4 = 1 (mod y): sequence gives values of n such x^4 = 1 (mod n) has no solution 1 < x < n-1.
%C A066499 k is of the form p^m or 2*p^m where p is A002145 (with the exception of a(2)=4).
%C A066499 All prime numbers here belong also to A002145, prime numbers of the form 4n+3. - _Enrique Pérez Herrero_, Sep 07 2011
%D A066499 W. J. LeVeque, Fundamentals of Number Theory, pp. 57 Problem 15, Dover NY 1996.
%H A066499 Harry J. Smith, <a href="/A066499/b066499.txt">Table of n, a(n) for n = 1..1000</a>
%t A066499 Select[Range[300],Mod[EulerPhi[#],4]==2&] (* _Harvey P. Dale_, Feb 18 2018 *)
%o A066499 (PARI) isok(k) = { eulerphi(k)%4 == 2 } \\ _Harry J. Smith_, Feb 18 2010
%Y A066499 Cf. A066498, A066500, A066501, A066502, A000010.
%Y A066499 Essentially the same as A097987.
%Y A066499 Cf. A002145.
%K A066499 nonn
%O A066499 1,1
%A A066499 _Benoit Cloitre_, Jan 04 2002
%E A066499 Simpler definition from _Lekraj Beedassy_, Jul 21 2003
%E A066499 Corrected and extended by _Ray Chandler_, Nov 06 2003