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A066828 Numbers n such that n divides the average of Prime(n-1) and Prime(n+1). 0
4, 5, 11, 12, 70, 72, 1053, 6459, 6460, 40083, 251742, 637320, 637322, 637330, 10553828, 69709721, 179992913, 179992922, 465769813, 1208198617, 1208198629, 3140421742, 3140421769, 3140421866, 8179002192, 8179002205, 8179002209 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Each cluster of candidates is about e (2.71828...) times as large as the previous one.

LINKS

Table of n, a(n) for n=1..27.

EXAMPLE

The average of p(4) = 7 and p(6) = 13 is 10, which is divisible by 5; so 5 is a term of the sequence.

MATHEMATICA

a = 0; b = 1; c = 2; Do[ c = Prime[ n + 1 ]; If[ IntegerQ[ (a + c)/(2n) ], Print[ n ] ]; a = b; b = c, {n, 1, 2 10^9} ]

CROSSREFS

Cf. A066706.

Sequence in context: A047374 A241653 A100107 * A163098 A216562 A174009

Adjacent sequences:  A066825 A066826 A066827 * A066829 A066830 A066831

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Jan 20 2002

STATUS

approved

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Last modified July 5 23:36 EDT 2020. Contains 335475 sequences. (Running on oeis4.)