A145834 - OEIS

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A145834

a(n) = difference between the n-th composite number and the sum of its prime factors with repetition.

0, 1, 2, 3, 3, 5, 5, 7, 8, 10, 11, 11, 9, 15, 15, 11, 18, 17, 20, 22, 19, 15, 23, 26, 17, 23, 29, 30, 29, 34, 21, 37, 35, 38, 31, 35, 43, 39, 43, 35, 27, 48, 29, 50, 52, 47, 50, 47, 43, 56, 60, 35, 62, 53, 59, 60, 67, 69, 39, 70, 63, 41, 55, 71, 77, 71, 65, 59, 45, 71, 83, 82, 82 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,3`
	LINKS	`Table of n, a(n) for n=1..73.`
	FORMULA	`a(n) = A075255(A002808(n)) = A002808(n) - A001414(A002808(n)).`
	EXAMPLE	`a(1) = 4 - (2+2) = 0; a(2) = 6 - (2+3) = 1; a(3) = 8 - (2+2+2) = 2 ; a(4) = 9 - (3+3) = 3; a(5) = 10 - (2+5) = 3.`
	PROG	`(PARI) A145834(n)={for(k=0, primepi(n), isprime(n++)&k--); n+0-sum(i=1, #n=factor(n)~, n[1, i]*n[2, i])} \\ M. F. Hasler, Oct 31 2008`
	CROSSREFS	`Cf. A001414, A002808, A075255.` `Sequence in context: A159050 A210336 A280271 * A339246 A341142 A130006` `Adjacent sequences: A145831 A145832 A145833 * A145835 A145836 A145837`
	KEYWORD	`nonn`
	AUTHOR	`Alexander R. Povolotsky, Oct 20 2008`
	EXTENSIONS	`Edited and extended by Ray Chandler, Oct 24 2008`
	STATUS	`approved`

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Last modified April 11 09:24 EDT 2021. Contains 342886 sequences. (Running on oeis4.)