A105076 - OEIS

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A105076

Numbers k such that 60*k^2 + 60*k + 1 is a square.

0

0, 1, 2, 11, 19, 90, 153, 712, 1208, 5609, 9514, 44163, 74907, 347698, 589745, 2737424, 4643056, 21551697, 36554706, 169676155, 287794595, 1335857546, 2265802057, 10517184216, 17838621864, 82801616185, 140443172858, 651895745267

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..28.

FORMULA

From R. J. Mathar, Nov 13 2009: (Start)

a(n) = a(n-1) + 8*a(n-2) - 8*a(n-3) - a(n-4) + a(n-5).

G.f.: x^2*(1+x+x^2)/((1-x)*(x^4-8*x^2+1)). (End)

CROSSREFS

Cf. A103200, A001090.

Sequence in context: A067660 A235472 A217308 * A103200 A067670 A217071

Adjacent sequences: A105073 A105074 A105075 * A105077 A105078 A105079

KEYWORD

nonn

AUTHOR

Pierre CAMI, Apr 06 2005

EXTENSIONS

Partially edited by Jon E. Schoenfield, Oct 13 2019

STATUS

approved