The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A025321

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A025321

Numbers that are the sum of 3 nonzero squares in exactly 1 way.
(history; published version)

#36 by Charles R Greathouse IV at Mon Aug 05 09:45:56 EDT 2024

STATUS

editing

approved

#35 by Charles R Greathouse IV at Mon Aug 05 09:45:40 EDT 2024

PROG

(PARI) is(n)=if(n<11, return(n>0 && n%3==0)); if(n%4==0, return(is(n/4))); my(w); for(i=sqrtint((n-1)\3)+1, sqrtint(n-2), my(t=n-i^2); for(j=sqrtint((t-1)\2)+1, min(sqrtint(t-1), i), if(issquare(t-j^2), w++>1 && return(0)))); w \\ Charles R Greathouse IV, Aug 05 2024

STATUS

approved

editing

#34 by Alois P. Heinz at Fri Nov 03 06:41:24 EDT 2023

STATUS

reviewed

approved

#33 by Michel Marcus at Fri Nov 03 06:39:54 EDT 2023

STATUS

proposed

reviewed

#32 by Jon E. Schoenfield at Fri Nov 03 06:37:03 EDT 2023

STATUS

editing

proposed

#31 by Jon E. Schoenfield at Fri Nov 03 06:37:00 EDT 2023

LINKS

T. D. Noe and Donovan Johnson, <a href="/A025321/b025321.txt">Table of n, a(n) for n = 1..605</a> (terms < 10^8, ; first 417 terms from T. D. Noe)

Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquareNumber.html">Square Number.</a>.

STATUS

approved

editing

#30 by Susanna Cuyler at Fri Nov 06 08:37:27 EST 2020

STATUS

proposed

approved

#29 by Jean-François Alcover at Fri Nov 06 04:52:20 EST 2020

STATUS

editing

proposed

#28 by Jean-François Alcover at Fri Nov 06 04:52:16 EST 2020

MATHEMATICA

b[n_, i_, k_, t_] := b[n, i, k, t] = If[n == 0, If[t == 0, 1, 0], If[i<1 || t<1, 0, b[n, i - 1, k, t] + If[i^2 > n, 0, b[n - i^2, i, k, t - 1]]]];

T[n_, k_] := b[n, Sqrt[n] // Floor, k, k];

Position[Table[T[n, 3], {n, 0, 200}], 1] - 1 // Flatten (* Jean-François Alcover, Nov 06 2020, after Alois P. Heinz in A243148 *)

STATUS

approved

editing

#27 by Alois P. Heinz at Mon Feb 25 10:04:19 EST 2019

STATUS

editing

approved