A161992 Numbers which squared are a sum of 3 distinct nonzero squares.

7, 9, 11, 13, 14, 15, 17, 18, 19, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87

Offset

1,1

Comments

Square roots of squares in A004432. - R. J. Mathar, Sep 22 2009

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Example

7^2 = 2^2 + 3^2 + 6^2. 9^2 = 1^2 + 4^2 + 8^2. 11^2 = 2^2 + 6^2 + 9^2. 15^2 = 2^2 + 5^2 + 14^2.

Maple

isA004432 := proc(n) local x, y, z2 ; for x from 1 do if x^2 > n then break; fi; for y from 1 to x-1 do z2 := n-x^2-y^2 ; if z2 < y^2 and z2 > 0 then if issqr(z2) then RETURN(true) ; fi; fi; od: od: false ; end:
isA161992 := proc(n) isA004432(n^2) ; end:
for n from 1 do if isA161992(n) then printf("%d\n", n) ; fi; od: # R. J. Mathar, Sep 22 2009

Mathematica

lst={}; Do[Do[Do[a=(x^2+y^2+z^2)^(1/2); If[a==IntegerPart[a], AppendTo[lst, a]], {z, y+1, 2*5!}], {y, x+1, 2*5!}], {x, 5!}]; lst; q=Take[Union[%], 150]

Prog

(PARI) is(n) = n>>=valuation(n, 2); n > 5 \\ David A. Corneth, Sep 18 2020

Crossrefs

Cf. A004432, A029747.

Sequence in context: A191883 A108815 A262536 * A334102 A167377 A360796

Adjacent sequences: A161989 A161990 A161991 * A161993 A161994 A161995

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Jun 24 2009

Extensions

Definition rephrased by R. J. Mathar, Sep 22 2009

Status

approved