A236711 Numbers that are the sum of 2 nonzero squares in exactly 11 ways.

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

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