A023741 Ternary expansion uses each positive digit just once.

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

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