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A306358 Odd numbers which are the sum of two squares in two or more different ways. 1
25, 65, 85, 125, 145, 169, 185, 205, 221, 225, 265, 289, 305, 325, 365, 377, 425, 445, 481, 485, 493, 505, 533, 545, 565, 585, 625, 629, 685, 689, 697, 725, 745, 765, 785, 793, 841, 845, 865, 901, 905, 925, 949, 965, 985, 1025, 1037, 1073, 1105, 1125, 1145, 1157, 1165, 1189, 1205, 1225, 1241 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Odd terms of A118882.

Odd numbers k such that A000161(k) >= 2.

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

The decompositions of the first terms are

25: [[4, 3], [5, 0]]

65: [[7, 4], [8, 1]]

85: [[7, 6], [9, 2]]

125: [[10, 5], [11, 2]]

145: [[9, 8], [12, 1]]

169: [[12, 5], [13, 0]]

185: [[11, 8], [13, 4]]

205: [[13, 6], [14, 3]]

221: [[11, 10], [14, 5]]

225: [[12, 9], [15, 0]]

265: [[12, 11], [16, 3]]

289: [[15, 8], [17, 0]]

305: [[16, 7], [17, 4]]

325: [[15, 10], [17, 6], [18, 1]]

365: [[14, 13], [19, 2]]

377: [[16, 11], [19, 4]]

PROG

(PARI) A000161(n)=sum(k=sqrtint((n-1)\2)+1, sqrtint(n), issquare(n-k^2));

is(n)=if(n%2==1, A000161(n)>1, 0);

select(is, vector(1300, n, n))

CROSSREFS

Sequence in context: A061970 A159008 A183373 * A120961 A285579 A050993

Adjacent sequences:  A306355 A306356 A306357 * A306359 A306360 A306361

KEYWORD

nonn

AUTHOR

Joerg Arndt, Feb 10 2019

STATUS

approved

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Last modified February 23 14:22 EST 2020. Contains 332160 sequences. (Running on oeis4.)