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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A271184 Löschian numbers (A003136) of the form k^2+1. 1
1, 37, 325, 577, 1297, 2917, 3601, 4357, 7057, 8101, 9217, 14401, 15877, 22501, 24337, 28225, 32401, 41617, 44101, 46657, 57601, 60517, 69697, 72901, 79525, 86437, 90001, 93637, 108901, 133957, 147457, 156817, 176401, 197137, 202501, 219025, 224677, 236197, 291601, 298117, 318097 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Intersection of A002522 and A003136.

Corresponding values of k are 0, 6, 18, 24, 36, 54, 60, 66, 84, 90, 96, 120, 126, 150, 156, 168, 180, 204, 210, 216, 240, 246, 264, 270, 282, 294, 300, 306, ...

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

37 is a term because 37 = 6^2 + 1 = 4^2 + 4*3 + 3^2.

MATHEMATICA

Select[Range[10^6], And[IntegerQ@Sqrt[# - 1], Resolve[Exists[{x, y}, Reduce[# == x^2 + x y + y^2, {x, y}, Integers]]]] &] (* Michael De Vlieger, Apr 01 2016 *)

PROG

(PARI) is(n) = #bnfisintnorm(bnfinit(z^2+z+1), n);

for(k=0, 2000, if(is(n=k^2+1), print1(n, ", ")));

CROSSREFS

Cf. A002522, A003136.

Sequence in context: A114785 A061014 A130450 * A217117 A291859 A133554

Adjacent sequences:  A271181 A271182 A271183 * A271185 A271186 A271187

KEYWORD

nonn

AUTHOR

Altug Alkan, Apr 01 2016

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 2 08:02 EDT 2020. Contains 335398 sequences. (Running on oeis4.)