The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A243680 Nonnegative integers of the form 2x^2+xy+5y^2. 1
 0, 2, 5, 6, 8, 11, 15, 18, 20, 24, 26, 32, 33, 41, 44, 45, 47, 50, 54, 59, 60, 65, 71, 72, 78, 80, 83, 86, 89, 96, 98, 99, 104, 110, 122, 123, 125, 128, 132, 135, 137, 141, 143, 149, 150, 158, 162, 164, 167, 176, 177, 180, 188, 195, 197, 200, 206, 213, 215, 216, 227, 234, 236, 239, 240, 242, 245 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Discriminant -39. LINKS N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references) MAPLE fd:=proc(a, b, c, M) local dd, xlim, ylim, x, y, t1, t2, t3, t4, i; dd:=4*a*c-b^2; if dd<=0 then error "Form should be positive definite."; break; fi; t1:={}; xlim:=ceil( sqrt(M/a)*(1+abs(b)/sqrt(dd))); ylim:=ceil( 2*sqrt(a*M/dd)); for x from 0 to xlim do for y from -ylim to ylim do t2 := a*x^2+b*x*y+c*y^2; if t2 <= M then t1:={op(t1), t2}; fi; od: od: t3:=sort(convert(t1, list)); t4:=[]; for i from 1 to nops(t3) do if isprime(t3[i]) then t4:=[op(t4), t3[i]]; fi; od: [[seq(t3[i], i=1..nops(t3))], [seq(t4[i], i=1..nops(t4))]]; end; fd(2, 1, 5, 500); CROSSREFS Primes: A106886. Sequence in context: A026179 A300063 A230902 * A280381 A105107 A002253 Adjacent sequences:  A243677 A243678 A243679 * A243681 A243682 A243683 KEYWORD nonn AUTHOR N. J. A. Sloane, Jun 08 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 21 05:23 EST 2020. Contains 332086 sequences. (Running on oeis4.)