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A049457 Least positive integer k such that the number having periodic continued fraction [ 1,m,1,m,1,m,... ] is of form (a+b*sqrt(k))/c, where a,b,c are positive integers. 0
5, 3, 21, 2, 5, 15, 77, 6, 13, 35, 165, 3, 221, 7, 285, 5, 357, 11, 437, 30, 21, 143, 69, 42, 29, 195, 93, 14, 957, 255, 1085, 2, 1221, 323, 1365, 10, 1517, 399, 1677, 110, 205, 483, 2021, 33, 5, 23, 2397, 39, 53, 3, 2805, 182, 3021, 87, 3245, 210, 3477, 899, 413 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Squarefree factors of k^2+2k-3. - Artur Jasinski, May 19 2008

LINKS

Table of n, a(n) for n=1..59.

FORMULA

Least positive integer of the form m(m+4)/(w^2), where m and w are positive integers.

PROG

(PARI) a(n)=if(n<1, 0, core(n^2+4*n))

CROSSREFS

Sequence in context: A256565 A298098 A248256 * A061037 A070262 A171621

Adjacent sequences:  A049454 A049455 A049456 * A049458 A049459 A049460

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

More terms from Michael Somos, Oct 28, 2002

STATUS

approved

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Last modified December 11 21:28 EST 2019. Contains 329937 sequences. (Running on oeis4.)