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A088836 a(n) = (A020639(2n+1) + A006530(2n+1))/2, arithmetic mean of max and min prime factor applied to odd numbers (i.e., when this mean is integer). 2
3, 5, 7, 3, 11, 13, 4, 17, 19, 5, 23, 5, 3, 29, 31, 7, 6, 37, 8, 41, 43, 4, 47, 7, 10, 53, 8, 11, 59, 61, 5, 9, 67, 13, 71, 73, 4, 9, 79, 3, 83, 11, 16, 89, 10, 17, 12, 97, 7, 101, 103, 5, 107, 109, 20, 113, 14, 8, 12, 11, 22, 5, 127, 23, 131, 13, 4, 137, 139, 25, 12, 17, 5, 149, 151 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

EXAMPLE

If 2n+1 is prime then a(2n+1) = 2n + 1.

MATHEMATICA

Table[(FactorInteger[2 n + 1][[1, 1]] + FactorInteger[2 n + 1][[-1, 1]])/2, {n, 75}] (* Michael De Vlieger, Mar 28 2015 *)

CROSSREFS

Cf. A020639, A006530.

Sequence in context: A326577 A090368 A120374 * A076565 A286517 A199423

Adjacent sequences:  A088833 A088834 A088835 * A088837 A088838 A088839

KEYWORD

nonn

AUTHOR

Labos Elemer, Oct 31 2003

STATUS

approved

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Last modified December 7 05:14 EST 2019. Contains 329839 sequences. (Running on oeis4.)