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

Author

Vladimir Joseph Stephan Orlovsky, Jun 24 2009

Keywords

• nonn

Comments

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

Examples

			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.
		

Links

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

Crossrefs

Cf. A004432, A029747.

Programs

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]

PARI

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

Extensions

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