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!)
A239527 Numbers k^2 + (k+1)^2 that can be expressed as a sum of two squares in exactly one other way. 1
85, 145, 221, 265, 365, 481, 545, 685, 1405, 1513, 1985, 2245, 2813, 2965, 3281, 3785, 3961, 4141, 4705, 5305, 5513, 5941, 6161, 6385, 6613, 7081, 7813, 8065, 8321, 9113, 9385, 10805, 11101, 11401, 11705, 12013, 12961, 13285, 13945, 16021, 17113, 17861, 19405 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A166080.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..10000

FORMULA

Each number is of the form 2y^2 + 2y + 1.

EXAMPLE

365 is in the sequence because 365 = 2^2+19^2 = 13^2+14^2; in the second representation 14-13=1.

MATHEMATICA

ok[n_] := 2 == Count[ PowersRepresentations[n, 2, 2], _?(! MemberQ[#, 0] &)]; Select[(2*#^2 + 2*# + 1) & /@ Range[100], ok] (* Giovanni Resta, Mar 21 2014 *)

CROSSREFS

Cf. A166080, A000404, A001844.

Sequence in context: A027453 A259219 A273123 * A029471 A083750 A043684

Adjacent sequences:  A239524 A239525 A239526 * A239528 A239529 A239530

KEYWORD

nonn

AUTHOR

Carmine Suriano, Mar 21 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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 05:51 EDT 2020. Contains 337897 sequences. (Running on oeis4.)