id:A080942 - OEIS Search Results

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Number of divisors of n that are also suffices of n in binary representation.

+0
9

1, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 1, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 4, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`a(n)=1 iff n=2^k (A000079), the only divisor is n itself;` `for a(n)>1 the other trivial divisor is 1 for odd numbers and 2 for even numbers (A057716);` `a(A080943(n))=2; a(A080945(n))>2; a(A080946(n))=3; a(A080947(n))>3;` `a(n) <= A000005(n); for odd primes p: a(p)=2;` `a(A080948(n))=n and a(m)<n for m<A080948(n).`
	EXAMPLE	`n=63 has A000005(63)=6 divisors: 1='1', 3='11', 7='111', 9='1001', 21='10101' and 63='111111', {1,11,111,111111} are also suffices of 111111, therefore a(63)=4."`
	CROSSREFS	`Cf. A007088, A080948, A080940, A080941.` `Sequence in context: A070304 A083952 A043529 this_sequence A099812 A068068 A092505` `Adjacent sequences: A080939 A080940 A080941 this_sequence A080943 A080944 A080945`
	KEYWORD	`nonn,base`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 25 2003`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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