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A075839 11*n^2 - 2 is a square. +0
6
1, 19, 379, 7561, 150841, 3009259, 60034339, 1197677521, 23893516081, 476672644099, 9509559365899, 189714514673881, 3784780734111721, 75505900167560539, 1506333222617099059, 30051158552174420641 (list; graph; listen)
OFFSET

0,2

COMMENT

Lim. n -> inf. a(n)/a(n-1) = 10 + 3*sqrt(11).

REFERENCES

A. H. Beiler, "The Pellian", ch. 22 in Recreations in the Theory of Numbers: The Queen of Mathematics Entertains. Dover, New York, New York, pp. 248-268, 1966.

L. E. Dickson, History of the Theory of Numbers, Vol. II, Diophantine Analysis. AMS Chelsea Publishing, Providence, Rhode Island, 1999, p. 341-400.

Peter G. L. Dirichlet, Lectures on Number Theory (History of Mathematics Source Series, V. 16); American Mathematical Society, Providence, Rhode Island, 1999, p. 139-147.

LINKS

Index entries for two-way infinite sequences

Index entries for sequences related to linear recurrences with constant coefficients

Tanya Khovanova, Recursive Sequences

J. J. O'Connor and E. F. Robertson, Pell's Equation

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

FORMULA

a(n) = ((3+sqrt(11))*(10+3*sqrt(11))^n - (3-sqrt(11))*(10-3*sqrt(11))^n)/(2*sqrt(11)). - Dean Hickerson (dean.hickerson(AT)yahoo.com), Dec 09 2002

G.f.: (1-x)/(1-20*x+x^2). a(n)=20*a(n-1)-a(n-2), n>1. - Michael Somos, Oct 29 2002

Let q(n, x)=sum(i=0, n, x^(n-i)*binomial(2*n-i, i)) then a(n)=q(n, 18). - Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 06 2002

G.f.: (1-x)/(1-20*x+x^2). a(n)=20*a(n-1)-a(n-2). a(-1-n)=a(n). - Michael Somos, Apr 18 2003

PROGRAM

(PARI) a(n)=subst(poltchebi(n+1)+poltchebi(n), x, 10)/11

CROSSREFS

11a(n)^2-9*A083043(n)^2=2.

Row 20 of array A094954.

Cf. A075844.

Sequence in context: A057685 A041686 A023283 this_sequence A158592 A072359 A094737

Adjacent sequences: A075836 A075837 A075838 this_sequence A075840 A075841 A075842

KEYWORD

easy,nonn

AUTHOR

Gregory V. Richardson (omomom(AT)hotmail.com), Oct 14 2002

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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