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A048688 Number of classes generated by function A000005 when applied to binomial coefficients. 1
1, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 5, 8, 6, 6, 8, 9, 6, 11, 7, 11, 10, 10, 9, 11, 11, 11, 10, 15, 13, 15, 11, 15, 16, 14, 14, 16, 15, 15, 12, 18, 17, 18, 12, 22, 18, 20, 19, 21, 17, 20, 19, 24, 21, 21, 15, 25, 19, 18, 19, 24, 21, 28, 25, 26, 24, 29, 19, 29, 25, 24, 26, 29, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = length(union(A000005(binomial(n,k)))), for 0<= k <= n.

EXAMPLE

For n=9 A000005({C(9,k)})={1,3,9,12,12,12,12,9,3,1} includes 4 distinct values so generating 4 classes of k values: {0,9},{1,8},{2,7} and {3,4,5,6}. So a(9)=4.

MATHEMATICA

Table[Length[Union[Table[DivisorSigma[0, Binomial[n, k]], {k, 0, n}]]], {n, 1, 50}] (* G. C. Greubel, May 19 2017 *)

CROSSREFS

Cf. A000005, A001221, A007947.

Sequence in context: A196383 A074198 A196169 * A092695 A281687 A033270

Adjacent sequences:  A048685 A048686 A048687 * A048689 A048690 A048691

KEYWORD

nonn

AUTHOR

Labos Elemer

STATUS

approved

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Last modified January 17 22:51 EST 2019. Contains 319251 sequences. (Running on oeis4.)