id:A158601 - OEIS Search Results

Search: id:A158601

Displaying 1-1 of 1 results found.

page 1

a(n)=20*(20*n^2+1).

+0
2

20, 420, 1620, 3620, 6420, 10020, 14420, 19620, 25620, 32420, 40020, 48420, 57620, 67620, 78420, 90020, 102420, 115620, 129620, 144420, 160020, 176420, 193620, 211620, 230420, 250020, 270420, 291620, 313620, 336420, 360020, 384420, 409620 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`The identity (40n^2+1)^2 - (400n^2+20)(2n)^2 = 1 can be written in` `Pell-format as (A158602(n))^2 - a(n)* (A005843(n))^2 =1.`
	LINKS	`Vincenzo Librandi, X^2-AY^2=1` `Edward Everett Withford, Pell Equation` `Wolfram MathWorld, Pell Equation`
	FORMULA	`a(n)= 3a(n-1) -3a(n-2) +a(n-3). G.f.: -20(1+18x+21*x^2)/(x-1)^3.`
	CROSSREFS	`Cf. A005843, A158602` `Sequence in context: A041181 A041762 A068772 this_sequence A130832 A109116 A136257` `Adjacent sequences: A158598 A158599 A158600 this_sequence A158602 A158603 A158604`
	KEYWORD	`nonn,easy`
	AUTHOR	`Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 22 2009`
	EXTENSIONS	`Comment rewritten, formula replaced by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 28 2009`

page 1

Search completed in 0.002 seconds

Last modified December 17 13:29 EST 2009. Contains 170826 sequences.

AT&T Labs Research