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A062854 First differences of A027424. 10
1, 2, 3, 3, 5, 4, 7, 5, 6, 6, 11, 6, 13, 8, 9, 8, 17, 9, 19, 10, 12, 12, 23, 10, 16, 14, 15, 13, 29, 12, 31, 15, 18, 18, 20, 13, 37, 20, 21, 16, 41, 17, 43, 20, 21, 24, 47, 17, 31, 22, 27, 23, 53, 22, 31, 22, 30, 30, 59, 19, 61, 32, 28, 26, 36, 26, 67, 30, 36, 26, 71, 23, 73, 38 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For prime p, a(p) = p. - Ralf Stephan, Jun 02 2005

a(n) is the number of times n appears in A033677. - Franklin T. Adams-Watters, Nov 18 2005

Conjecture: a(n) > n/log(n) for n > 2. - Thomas Ordowski, Jan 28 2017

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

EXAMPLE

a(4)=3 because there are 9 unique products in the 4 X 4 multiplication table (1 2 3 4 6 8 9 12 16), which is 3 more than the 6 unique products in the 3 X 3 multiplication table (1 2 3 4 6 9).

MATHEMATICA

Prepend[Differences@ #, First@ #] &@ Module[{ u = {}}, Table[Length[u = Union[u, n Range@ n]], {n, 100}]] (* Michael De Vlieger, Jan 30 2017 *)

PROG

(PARI) b(n) = #setbinop((x, y)->x*y, vector(n, i, i); );

a(n) = b(n) - b(n-1); \\ Michel Marcus, Jan 28 2017

CROSSREFS

Cf. A027421, A062854, A062855, A062856, A062857, A062859.

Sequence in context: A119674 A064920 A064916 * A057859 A242992 A029579

Adjacent sequences:  A062851 A062852 A062853 * A062855 A062856 A062857

KEYWORD

nonn

AUTHOR

Ron Lalonde (ronronronlalonde(AT)hotmail.com), Jun 25 2001

EXTENSIONS

More terms from Ralf Stephan, Jun 02 2005

STATUS

approved

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Last modified July 11 08:10 EDT 2020. Contains 335626 sequences. (Running on oeis4.)