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A106330
Numbers k such that k^2 = 24*(j^2) + 25.
1
5, 7, 11, 25, 59, 103, 245, 583, 1019, 2425, 5771, 10087, 24005, 57127, 99851, 237625, 565499, 988423, 2352245, 5597863, 9784379, 23284825, 55413131, 96855367, 230496005, 548533447, 958769291, 2281675225, 5429921339, 9490837543, 22586256245, 53750679943
OFFSET
1,1
COMMENTS
The ratio k(n) /(2*j(n)) tends to sqrt(6) as n increases.
FORMULA
Recurrence: k(1)=5, k(2)=7, k(3)=11, k(4)=25, k(5)=10*k(2)-k(3), k(6)=10*k(3)-k(2) then k(n)=10*k(n-3)-k(n-6).
G.f.: (-7x^5-11x^4-25x^3+11x^2+7x+5)/(x^6-10x^3+1).
a(3n+1) = 5*A001079(n), a(3n+2) = A077409(n), a(3n+3) = A077250(n).
PROG
(PARI) Vec(-x*(7*x^5+11*x^4+25*x^3-11*x^2-7*x-5)/(x^6-10*x^3+1) + O(x^100)) \\ Colin Barker, Apr 16 2014
CROSSREFS
Cf. A106331.
Sequence in context: A067289 A036491 A036490 * A057247 A157437 A213677
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Apr 29 2005
EXTENSIONS
More terms, g.f. and formulas from Ralf Stephan, Nov 15 2010
More terms from Colin Barker, Apr 16 2014
STATUS
approved