A076690 Nearest integer to average of the smallest and largest prime factors of n (0.5 is rounded to 1).

2, 3, 2, 5, 3, 7, 2, 3, 4, 11, 3, 13, 5, 4, 2, 17, 3, 19, 4, 5, 7, 23, 3, 5, 8, 3, 5, 29, 4, 31, 2, 7, 10, 6, 3, 37, 11, 8, 4, 41, 5, 43, 7, 4, 13, 47, 3, 7, 4, 10, 8, 53, 3, 8, 5, 11, 16, 59, 4, 61, 17, 5, 2, 9, 7, 67, 10, 13, 5, 71, 3, 73, 20, 4, 11, 9, 8, 79, 4, 3, 22, 83, 5, 11, 23, 16

Offset

2,1

Links

Table of n, a(n) for n=2..87.

Example

The smallest and largest prime factors of 6 are 2 and 3, respectively, the average of which is 2.5, rounding off to 3. Hence a(6) = 3.

Mathematica

f[n_] := Module[{p, l}, p = Transpose[FactorInteger[n]][[1]]; l = Length[p]; Ceiling[(p[[1]] + p[[l]])/2]]; Table[f[i], {i, 2, 100}]

Crossrefs

Sequence in context: A079870 A364156 A185642 * A262549 A086287 A253236

Adjacent sequences: A076687 A076688 A076689 * A076691 A076692 A076693

Keyword

easy,nonn

Author

Joseph L. Pe, Oct 25 2002

Status

approved