login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A216278 Number of solutions to the equation x^2+2y^2 = n with x and y > 0. 2
0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 2, 0, 0, 0, 0, 0, 2, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 2, 0, 0, 2, 0, 0, 2, 0, 1, 0, 0, 0, 0, 0, 0, 2, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 2, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 3, 0, 0, 2, 0, 0, 0, 0, 1, 2, 0, 0, 0, 0, 1, 2, 0, 0, 0, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,27

LINKS

Table of n, a(n) for n=1..120.

MATHEMATICA

r[n_] := Reduce[x > 0 && y > 0 && x^2 + 2 y^2 == n, Integers];

a[n_] := Which[rn = r[n]; rn === False, 0, Head[rn] === And, 1, Head[rn] === Or, Length[rn], True, -1];

Table[a[n], {n, 1, 120}] (* Jean-Fran├žois Alcover, Jun 24 2017 *)

CROSSREFS

Cf. A092573, A119395, A000161, A025426.

Sequence in context: A036272 A257403 A083339 * A133827 A176192 A028633

Adjacent sequences:  A216275 A216276 A216277 * A216279 A216280 A216281

KEYWORD

nonn,changed

AUTHOR

V. Raman, Sep 03 2012

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified June 28 17:12 EDT 2017. Contains 288839 sequences.