A020335 Numbers whose base-7 representation is the juxtaposition of two identical strings.

8, 16, 24, 32, 40, 48, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150, 2200, 2250, 2300, 2350

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = n*7^floor(log_7(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018

Example

450_10 = 1212_7. - Jon E. Schoenfield, Feb 12 2021

Mathematica

a[n_] := n + n*7^Floor[Log[7, n] + 1]; Array[a, 50] (* Amiram Eldar, Apr 06 2021 *)

Crossrefs

Cf. A020330, A020331, A020332, A020333, A020334, A020336, A020337, A020338.

Sequence in context: A033020 A108651 A031488 * A044833 A033005 A072066

Adjacent sequences: A020332 A020333 A020334 * A020336 A020337 A020338

Keyword

nonn,base

Author

David W. Wilson, Melia Aldridge (ma38(AT)spruce.evansville.edu)

Status

approved