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Square elements of A046949.
0

%I #20 May 07 2021 19:52:58

%S 1,25,49,169,625,1369,3025,7921,18769,37249,208849,3485689,4950625,

%T 7756225,225150025,48195616225,264353307409,453673643809,

%U 1278932548201,5225490897028249,6290436331177441,16712972707067569

%N Square elements of A046949.

%t Join[{1}, Table[ 24*Sum[ d*Mod[d, 2], {d, Divisors[n]}], {n, 1, 10^6}]] // Accumulate // Select[#, IntegerQ[Sqrt[#]] &] & (* _Jean-François Alcover_, Jul 02 2013 *)

%o (PARI) B=1; print1(B, ", "); for (n=1,200000,t1=divisors(2*n); t2=0; for (i=1, length(t1), if( t1[ i ]%4 <> 0, t2=t2+t1[ i ])); B=B+8*t2; if (issquare(B), print1(B, ", ")))

%K nonn,nice,more

%O 0,2

%A _N. J. A. Sloane_

%E a(17)-a(18) from _Jason Earls_, Jul 21 2001

%E a(19)-a(21) from _Sean A. Irvine_, May 07 2021