

A161599


The list of the B values in the common solutions to the 2 equations 15*k + 1 = A^2, 19*k + 1 = B^2.


3



1, 18, 305, 5167, 87534, 1482911, 25121953, 425590290, 7209912977, 122142930319, 2069219902446, 35054595411263, 593858902089025, 10060546740102162, 170435435679647729, 2887341859813909231, 48914376181156809198, 828657053219851847135, 14038255528556324592097
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OFFSET

1,2


COMMENTS

The case C=15 of finding k such that C*k+1 and (C+4)*k+2 are both perfect squares (A160682).
The 2 equations are equivalent to the Pell equation x^2  285*y^2 = 1, with x = (285*k+17)/2 and y = A*B/2.


LINKS

Table of n, a(n) for n=1..19.
Andersen, K., Carbone, L. and Penta, D., KacMoody Fibonacci sequences, hyperbolic golden ratios, and real quadratic fields, Journal of Number Theory and Combinatorics, Vol 2, No. 3 pp 245278, 2011. See Section 9.
Index entries for linear recurrences with constant coefficients, signature (17, 1).


FORMULA

B(t+2) = 17*B(t+1)  B(t).
B(t) = ((285+19*w)*((17+w)/2)^(t1)+(28519*w)*((17w)/2)^(t1))/570 where w=sqrt(285).
G.f.: (1+x)*x/(117*x+x^2).


MAPLE

t:=0: for b from 1 to 1000000 do a:=sqrt((15*b^2+4)/19):
if (trunc(a)=a) then t:=t+1: n:=(b^21)/19: print(t, a, b, n): end if: end do:


PROG

(Sage) [(lucas_number2(n, 17, 1)lucas_number2(n1, 17, 1))/15 for n in range(1, 20)] # Zerinvary Lajos, Nov 10 2009


CROSSREFS

Cf. A160682, A161595 (sequence of A), A161583 (sequence of k).
Sequence in context: A228606 A228605 A193317 * A273434 A083451 A162804
Adjacent sequences: A161596 A161597 A161598 * A161600 A161601 A161602


KEYWORD

nonn


AUTHOR

Paul Weisenhorn, Jun 14 2009


EXTENSIONS

Edited, extended by R. J. Mathar, Sep 02 2009


STATUS

approved



