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A024639 n written in fractional base 7/2. 2
0, 1, 2, 3, 4, 5, 6, 20, 21, 22, 23, 24, 25, 26, 40, 41, 42, 43, 44, 45, 46, 60, 61, 62, 63, 64, 65, 66, 210, 211, 212, 213, 214, 215, 216, 230, 231, 232, 233, 234, 235, 236, 250, 251, 252, 253, 254, 255, 256, 400, 401, 402, 403, 404, 405, 406, 420, 421, 422, 423, 424, 425 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..61.

FORMULA

To represent a number in base 7, if a digit exceeds 6, subtract 7 and carry 1. In the fractional base 7/2, subtract 7 and carry 2.

EXAMPLE

From Alonso del Arte, Apr 21 2019: (Start)

The integers 0 through 6 are written with the digits 0 through 6.

Then, since b = 7/2 is written as 10, and 7 is twice 7/2, 7 is 20 in base 7/2, and therefore a(7) = 20.

a(28) = 210 since 2 * (7/2)^2 + 1 * (7/2) = 2 * 49/4 + 1 * 7/2 = 98/4 + 14/4 = 112/4 = 28.

(End)

MATHEMATICA

Select[Table[FromDigits[IntegerDigits[n, 7]], {n, 0, 230}], IntegerQ[FromDigits[IntegerDigits[#], 7/2]] &] (* Alonso del Arte, Apr 21 2019 *)

CROSSREFS

Cf. A000079, A000420, A007093.

Sequence in context: A264975 A031015 A329581 * A123678 A208450 A037333

Adjacent sequences:  A024636 A024637 A024638 * A024640 A024641 A024642

KEYWORD

nonn,base

AUTHOR

David W. Wilson

STATUS

approved

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Last modified November 27 15:36 EST 2021. Contains 349394 sequences. (Running on oeis4.)