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A274567 Least number k such that k^2-1 is the sum of two nonzero squares in exactly n ways. 2
3, 81, 51, 291, 1251, 339, 62499, 1971, 5201, 5001, 175781251, 7299 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(11) > 25*10^5 if it exists. - Chai Wah Wu, Jul 23 2020

From David A. Corneth, Jul 23 2020: (Start)

a(13) <= 17578125001, a(17) <= 610351562499. (End)

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

a(2) = 81 because 81^2 - 1 = 28^2 + 76^2 = 44^2 + 68^2.

CROSSREFS

Cf. A000404, A005563, A016032, A025426, A050795, A050797, A054994.

Sequence in context: A183265 A233124 A251694 * A137994 A074386 A116009

Adjacent sequences:  A274564 A274565 A274566 * A274568 A274569 A274570

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Jun 28 2016

EXTENSIONS

a(10) from Chai Wah Wu, Jul 22 2020

STATUS

approved

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Last modified October 16 15:22 EDT 2021. Contains 348042 sequences. (Running on oeis4.)