

A072818


Possibly the only integers of the form sqrt(m^2*(m^21)*2/3) [only checked for the first 5 terms].


2



0, 20, 1960, 192060, 18819920, 1844160100, 180708869880, 17707625088140, 1735166549767840, 170028614252160180, 16661069030161929800, 1632614736341616960220, 159979583092448300171760
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OFFSET

0,2


COMMENTS

These are the standard deviations of time for a random walk starting at 0 to reach one of the boundaries at +A001079(n) or A001079(n) for the first time.


LINKS

Indranil Ghosh, Table of n, a(n) for n = 0..501
Tanya Khovanova, Recursive Sequences
Index entries for linear recurrences with constant coefficients, signature (98, 1).


FORMULA

a(n) = 98*a(n1)a(n2) [starting with a(0)=0 and a(1)=20] =sqrt(A072819(A001079(n))).
a(n) = (1/12)*[49+20*sqrt(6)]^n*sqrt(6)(1/12)*sqrt(6)*[4920*sqrt(6)]^n, with n>=0. [Paolo P. Lava, Oct 06 2008]
G.f.: 20x/(198x+x^2). [Philippe Deléham, Nov 18 2008]


EXAMPLE

0 and 20 are at the start of the sequence since m^2*(m^21)*2/3 (A072819) starts 0, 0, 8, 48, 160, 400, 840, 1568, ... and the only squares among these are 0 and 400 with square roots of 0 and 20.


CROSSREFS

Sequence in context: A246619 A222973 A267575 * A123479 A071152 A195622
Adjacent sequences: A072815 A072816 A072817 * A072819 A072820 A072821


KEYWORD

nonn


AUTHOR

Henry Bottomley, Jul 14 2002


STATUS

approved



