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A131982 Numbers n such that A131981(n) = n/2. 2
576, 584, 588, 592, 600, 1650, 1654, 3430, 3440, 3448, 3452, 3458, 3462, 3466, 3474, 3520, 3600, 3608, 3610 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that number of terms <= n of A116700 equals number of terms <= n of A131881.

Numbers n such that numbers of numbers that occur in the concatenation of 1,2,3...,n-1 equals numbers of numbers that do not occur in the concatenation of 1,2,3...,n-1.

There are no other terms <= 600000. The plots in the link strongly suggest that the sequence is complete.

LINKS

Table of n, a(n) for n=1..19.

Klaus Brockhaus, Plots of A131981(n)/n at various scales

EXAMPLE

A131981(n) < n/2 for 1 <=n < 576,

A131981(n) < n/2 for 576 < n < 584,

A131981(n) > n/2 for 584 < n < 588,

A131981(n) < n/2 for 588 < n < 592,

A131981(n) > n/2 for 592 < n < 600,

A131981(n) > n/2 for 600 < n < 1650,

A131981(n) > n/2 for 1650 < n < 1654,

A131981(n) < n/2 for 1654 < n < 3430,

A131981(n) > n/2 for 3430 < n < 3440,

..............

A131981(n) < n/2 for 3608 < n <= 3610,

A131981(n) > n/2 for 3610 < n <= 600000.

PROG

(JBASIC)

s$ = "" : c = 0 : d = 0

FOR n = 1 TO 4000

sn$ = str$(n)

IF instr(s$, sn$) > 0 THEN d = d+1 ELSE c = c+1

s$ = s$ + sn$ : IF c = d THEN print n ; ", ";

NEXT

CROSSREFS

Cf. A116700 (early bird numbers), A131881 (complement of A116700), A131981 (number of early bird numbers <= n), A105390 (number of Rollman numbers <= n), A105391 (numbers n such that A105390(n) = n/2).

Sequence in context: A069421 A136111 A199549 * A295017 A053969 A316486

Adjacent sequences:  A131979 A131980 A131981 * A131983 A131984 A131985

KEYWORD

nonn,base

AUTHOR

Klaus Brockhaus, Aug 15 2007

EXTENSIONS

Edited by Charles R Greathouse IV, Oct 28 2009

STATUS

approved

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Last modified March 31 17:36 EDT 2020. Contains 333151 sequences. (Running on oeis4.)