id:A131981 - OEIS Search Results

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A131981

Number of early bird numbers <= n.

+0
4

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 8, 9, 9, 10, 10, 10, 10, 10, 10, 11, 12, 13, 14, 14, 15, 15, 15, 15, 15, 16, 17, 18, 19, 20, 20, 21, 21, 21, 21, 22, 23, 24, 25, 26, 27, 27, 28, 28, 28, 29, 30, 31, 32 (list; graph; listen)

	OFFSET	`1,21`
	COMMENT	`a(n) = number of k such that A116700(k) <= n; a(n) = n - number of k such that A131881(k) <= n.` `A131982 gives numbers n such that a(n) = n/2, or numbers n such that (number of k such that A116700(k) <= n) = (number of k such that A131881(k) <= n).`
	LINKS	`K. Brockhaus, Table of n, a(n) for n = 1..6000` `K. Brockhaus, Plots of A131981(n)/n at various scales`
	EXAMPLE	`There are two early bird numbers <= 21, viz. 12 and 21, hence a(21) = 2.`
	PROGRAM	`(JBASIC)` `s$ = "" : d = 0` `FOR n = 1 TO 84` `sn$ = str$(n)` `IF instr(s$, sn$) > 0 THEN d = d+1` `s$ = s$ + sn$ : print d ; ", ";` `NEXT`
	CROSSREFS	`Cf. A116700 (early bird numbers), A131881 (complement of A116700), A132133 (number of n-digit terms of 131881), A105390 (number of Rollman numbers <= n), A131982 (numbers n such that A131981(n) = n/2).` `Sequence in context: A140474 A091195 A072375 this_sequence A130147 A096143 A025792` `Adjacent sequences: A131978 A131979 A131980 this_sequence A131982 A131983 A131984`
	KEYWORD	`nonn,base`
	AUTHOR	`Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Aug 15 2007`

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Last modified December 3 01:16 EST 2008. Contains 151161 sequences.

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