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A236711 Numbers that are the sum of 2 nonzero squares in exactly 11 ways. 1
5281250, 9031250, 21125000, 26281250, 36125000, 42781250, 47531250, 52531250, 81281250, 84500000, 87781250, 105125000, 116281250, 126953125, 144500000, 166015625, 166531250, 171125000, 190125000, 210125000, 236531250, 241340450, 247531250, 253906250, 258781250 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Are all terms multiples of 5?

The answer is "no"; 2789895602 = 2 * 13^6 * 17^2 is a term that is not a multiple of 5. Is it the first such term? - Zak Seidov, Jul 05 2015

a(152) = 2789895602 is the first term that is not divisible by 5. In the first 1000 terms, the only powers to which 5 appears as a factor are 0 (for 10 terms, beginning with a(152), after which the next does not occur until a(331)), 2 (for only 14 terms, the smallest of which is a(22) = 241340450 = 2 * 5^2 * 13^6), 6 (for 360 terms), and 10 (for the remaining 616 terms). - Jon E. Schoenfield, Jul 07 2015

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 1..1000

C. Rivera, Puzzle 62

EXAMPLE

5281250 = x^2 + y^2 with {x,y} = {71,2297}, {245,2285}, {325,2275}, {575,2225}, {875,2125}, {949,2093}, {1105,2015}, {1175,1975}, {1435,1795}, {1567,1681}, {1625,1625}.

CROSSREFS

Cf.  A000404, A016032, A025285-A025293.

Sequence in context: A294988 A183746 A183706 * A184782 A116105 A116128

Adjacent sequences:  A236708 A236709 A236710 * A236712 A236713 A236714

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 30 2014

EXTENSIONS

More terms from Jon E. Schoenfield, Jul 05 2015

STATUS

approved

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Last modified July 6 23:56 EDT 2020. Contains 335484 sequences. (Running on oeis4.)