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A106331 Numbers j such that 24*(j^2) + 25 = k^2. 2
0, 1, 2, 5, 12, 21, 50, 119, 208, 495, 1178, 2059, 4900, 11661, 20382, 48505, 115432, 201761, 480150, 1142659, 1997228, 4752995, 11311158, 19770519, 47049800, 111968921, 195707962, 465745005, 1108378052, 1937309101, 4610400250 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The ratio k(n) /(2*j(n)) tends to sqrt(6) as n increases

LINKS

Table of n, a(n) for n=1..31.

Index entries for linear recurrences with constant coefficients, signature (0,0,10,0,0,-1). [R. J. Mathar, May 22 2010]

FORMULA

j(1)=0, j(2)=1, j(3)=2, j(4)=5, j(5)=10*j(2)+j(3), j(6)=10*j(3)+j(2), j(7)=10*j(4)+j(1) then j(n)=10*j(n-3)-j(n-6).

a(n) = +10*a(n-3) -a(n-6). G.f.: x^2*(1+2*x+5*x^2+2*x^3+x^4)/(1-10*x^3+x^6). [R. J. Mathar, May 22 2010]

a(3*n+1) = 5*A004189(n), a(3*n+2) = A077251(n), a(3*n+3) = A077249(n). - Ralf Stephan, Nov 15 2010

CROSSREFS

Cf. A106330.

Sequence in context: A218904 A170927 A182201 * A116727 A116729 A048840

Adjacent sequences:  A106328 A106329 A106330 * A106332 A106333 A106334

KEYWORD

nonn,easy

AUTHOR

Pierre CAMI, Apr 29 2005

EXTENSIONS

More terms from Jon E. Schoenfield, May 16 2010

STATUS

approved

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Last modified October 23 17:37 EDT 2021. Contains 348215 sequences. (Running on oeis4.)