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Define f(n) = n - largest nontrivial divisor of n or f(n) = n-1 if n is a prime. Form a triangle in which the n-th row contains terms n, f(n), f(f(n), ... until a 1 is reached; sequence gives triangle read by rows.

+0
5

1, 2, 1, 3, 2, 1, 4, 2, 1, 5, 4, 2, 1, 6, 3, 2, 1, 7, 6, 3, 2, 1, 8, 4, 2, 1, 9, 6, 3, 2, 1, 10, 5, 4, 2, 1, 11, 10, 5, 4, 2, 1, 12, 6, 3, 2, 1, 13, 12, 6, 3, 2, 1, 14, 7, 6, 3, 2, 1, 15, 10, 5, 4, 2, 1, 16, 8, 4, 2, 1, 17, 16, 8, 4, 2, 1, 18, 9, 6, 3, 2, 1, 19, 18, 9, 6, 3, 2, 1, 20, 10, 5, 4, 2, 1 (list; graph; listen)

	OFFSET	`0,2`
	EXAMPLE	`Triangle begins:` `1` `2 1` `3 2 1` `4 2 1` `5 4 2 1` `6 3 2 1` `7 6 3 2 1` `8 4 2 1` `9 6 3 2 1` `10 5 4 2 1`
	MAPLE	`j := 1:a[1] := 1:for i from 2 to 50 do n := i:j := j+1:a[j] := n:while(n>1) do if isprime(n) then r := n-1: else r := n-n/ifactors(n)[2][1][1]; fi; n := r:j := j+1:a[j] := n: od:od:seq(a[k], k=1..j);`
	CROSSREFS	`Cf. A073933, A073934, A073935.` `Sequence in context: A128260 A083368 A112379 this_sequence A082404 A120885 A057058` `Adjacent sequences: A073929 A073930 A073931 this_sequence A073933 A073934 A073935`
	KEYWORD	`nonn,tabf`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 19 2002`
	EXTENSIONS	`More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Aug 23 2002`

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Last modified December 5 20:25 EST 2009. Contains 170428 sequences.

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