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A023741 Ternary expansion uses each positive digit just once. 1
5, 7, 11, 15, 19, 21, 29, 33, 45, 55, 57, 63, 83, 87, 99, 135, 163, 165, 171, 189, 245, 249, 261, 297, 405, 487, 489, 495, 513, 567, 731, 735, 747, 783, 891, 1215, 1459, 1461, 1467, 1485, 1539, 1701, 2189, 2193, 2205, 2241, 2349, 2673, 3645, 4375, 4377 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..2000

MATHEMATICA

Union[ Map[ Plus@@(Array[ (3^#)&, Length[ # ], 0 ]*#)&, Flatten[ Table[ Permutations[ Join[ Range[ 3-1 ], Array[ 0&, k ] ] ], {k, 0, 6} ], 1 ] ] ]

PROG

(PARI) a(n)=(1+(j(n)>=i(n)))*3^i(n)+(2-(j(n)>=i(n)))*3^(j(n)%i(n)) where i(n) = floor(1/2+sqrt(n)) and j(n) = n-1-2*binomial(i(n), 2) /* Michael Somos, Jun 03 2000 */

CROSSREFS

Sequence in context: A075317 A134643 A039001 * A096819 A032699 A073088

Adjacent sequences:  A023738 A023739 A023740 * A023742 A023743 A023744

KEYWORD

nonn,base,easy

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified September 22 09:47 EDT 2021. Contains 347606 sequences. (Running on oeis4.)