A073788 - OEIS

A073788

Numbers in base -7.

0, 1, 2, 3, 4, 5, 6, 160, 161, 162, 163, 164, 165, 166, 150, 151, 152, 153, 154, 155, 156, 140, 141, 142, 143, 144, 145, 146, 130, 131, 132, 133, 134, 135, 136, 120, 121, 122, 123, 124, 125, 126, 110, 111, 112, 113, 114, 115, 116, 100, 101, 102, 103, 104, 105

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

REFERENCES

D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, 1969, Vol. 2, p. 189.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 0..10000

Eric Weisstein's World of Mathematics, Negabinary

Prepared and presented by Matthew Szudzik of Wolfram Research, A Mathematica programming contest

MATHEMATICA

ToNegaBases[i_Integer, b_Integer] := FromDigits[ Rest[ Reverse[ Mod[ NestWhileList[(#1 - Mod[ #1, b])/-b &, i, #1 != 0 &], b]]]]; Table[ ToNegaBases[n, 7], {n, 0, 60}]

PROG

(Python)

def A073788(n):

s, q = '', n

while q >= 7 or q < 0:

q, r = divmod(q, -7)

if r < 0:

q += 1

r += 7

s += str(r)

return int(str(q)+s[::-1]) # Chai Wah Wu, Apr 09 2016

CROSSREFS