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A306104 Numbers that are the difference of two positive squares in at least four ways. 3
96, 105, 120, 135, 144, 160, 165, 168, 189, 192, 195, 216, 224, 225, 231, 240, 255, 264, 273, 280, 285, 288, 297, 312, 315, 320, 336, 345, 351, 352, 357, 360, 375, 384, 385, 399, 400, 405, 408, 416, 420, 429, 432, 435, 440, 441, 448, 455, 456, 459, 465, 480, 483, 495 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that A100073(n) >= 4; see there for more information & formulas.

LINKS

Table of n, a(n) for n=1..54.

Geoffrey Campbell, Numbers that are the difference of two squares in two or more ways, Number Theory Group on LinkedIn, July 8, 2018.

FORMULA

A306104 = { n = 2k+1 | A056924(n) > 3 } U { n = 4k | A056924(n/4) > 3 }.

MATHEMATICA

Select[Range@495, Length@ FindInstance[x^2 - y^2 == # && x>y>0, {x, y}, Integers, 4] == 4 &] (* Giovanni Resta, Jul 10 2018 *)

PROG

(PARI) select( is(n)=A100073(n)>3, [1..500])

CROSSREFS

Cf. A100073, A058957, A056924.

Subsequence of A306103, A306102 and A058957.

Sequence in context: A090221 A045528 A181470 * A257411 A175116 A153484

Adjacent sequences:  A306101 A306102 A306103 * A306105 A306106 A306107

KEYWORD

nonn

AUTHOR

Geoffrey B. Campbell and M. F. Hasler, Jul 10 2018

STATUS

approved

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Last modified November 20 18:21 EST 2019. Contains 329337 sequences. (Running on oeis4.)