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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 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.)