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A141458 a(n) = A000111(2n) + A000111(2n+1). 1
2, 3, 21, 333, 9321, 404313, 25071021, 2103118293, 229256855121, 31493764788273, 5321869241361621, 1084772760899990253, 262436014353765070521, 74338674113237083780233, 24371443829213227706941821, 9155506650374192400724494213, 3906927095300068860534174415521 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..100

FORMULA

a(2n) == 21 (mod 100), n>0.

a(n) = (2n)! * [x^(2n)] sec(x) + sec(x)^2. - Ira M. Gessel, Apr 18 2013

MAPLE

A000111 := proc(n) if n = 0 then 1; else 2^n*abs(euler(n, 1/2)+euler(n, 1) ); end if; end proc:

A141458 := proc(n) A000111(2*n)+A000111(2*n+1) ; end proc: # R. J. Mathar, Jul 07 2011

CROSSREFS

Sequence in context: A328734 A296254 A114749 * A080670 A288532 A073647

Adjacent sequences:  A141455 A141456 A141457 * A141459 A141460 A141461

KEYWORD

nonn

AUTHOR

Paul Curtz, Aug 08 2008

STATUS

approved

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Last modified July 5 04:30 EDT 2020. Contains 335459 sequences. (Running on oeis4.)