A274044 Squarefree numbers that are the sum of two squares in more than one way.

65, 85, 130, 145, 170, 185, 205, 221, 265, 290, 305, 365, 370, 377, 410, 442, 445, 481, 485, 493, 505, 530, 533, 545, 565, 610, 629, 685, 689, 697, 730, 745, 754, 785, 793, 865, 890, 901, 905, 949, 962, 965, 970, 985, 986, 1010, 1037, 1066, 1073, 1090, 1105, 1130, 1145

Offset

1,1

Comments

Squarefree numbers that are the sum of two nonzero squares in more than one way.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

A005117 INTERSECT A007692. - R. J. Mathar, Feb 01 2017

Example

65 is a term because 65 = 5*13 = 1^2 + 8^2 = 4^2 + 7^2.

Prog

(PARI) isA007692(n) = {nb = 0; lim = sqrtint(n); for (x=1, lim, if ((n-x^2 >= x^2) && issquare(n-x^2), nb++); ); nb >= 2; }
lista(nn) = for(n=1, nn, if(isA007692(n) && issquarefree(n), print1(n, ", ")));

Crossrefs

Cf. A005117, A007692, A020893.

Sequence in context: A165158 A084648 A224770 * A024409 A131574 A323272

Adjacent sequences: A274041 A274042 A274043 * A274045 A274046 A274047

Keyword

nonn

Author

Altug Alkan, Jun 07 2016

Status

approved