cp's OEIS Frontend

A279241 Let f(n) = 4*n^2 + 2*n + 41. The values |f(n)| are primes for all n in the range -20 to 19 (but not for n=-21 or 20). The sequence lists this maximal run of primes in the order in which they appear.

%I A279241 #15 Nov 22 2021 10:17:13
%S A279241 1601,1447,1301,1163,1033,911,797,691,593,503,421,347,281,223,173,131,
%T A279241 97,71,53,43,41,47,61,83,113,151,197,251,313,383,461,547,641,743,853,
%U A279241 971,1097,1231,1373,1523
%N A279241 Let f(n) = 4*n^2 + 2*n + 41. The values |f(n)| are primes for all n in the range -20 to 19 (but not for n=-21 or 20). The sequence lists this maximal run of primes in the order in which they appear.
%C A279241 This same list will also appear for 0<=x<=39 using the form 4x^2-158x+1601.
%C A279241 The substitution 2n = m changes this quadratic form into Euler's famous quadratic form m^2+m+41 (see A005846). Concerning the conjectured extremal properties of these forms, one should note the comment from _T. D. Noe_ in A005846. For another quadratic form similar to this one, see A145096. - _N. J. A. Sloane_, Dec 17 2016
%p A279241 s1:=[]; f:=n->4*n^2+2*n+41;
%p A279241 for n from -20 to 19 do if isprime(abs(f(n))) then s1:=[op(s1), abs(f(n))]; fi; od:
%p A279241 s1; # From _N. J. A. Sloane_, Dec 17 2016. This does nothing more than produce the primes mentioned in the definition
%Y A279241 Cf. A005846, A014556, A145096.
%K A279241 fini,nonn
%O A279241 1,1
%A A279241 _Charles Kusniec_, Dec 08 2016
%E A279241 Edited by _N. J. A. Sloane_, Dec 17 2016