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A187026 Least m such that prime(n) divides (prime(m) + prime(m+1))/2. 1
2, 3, 6, 8, 25, 9, 11, 21, 19, 69, 24, 29, 46, 23, 60, 115, 51, 111, 32, 82, 129, 185, 132, 71, 106, 155, 63, 116, 84, 203, 54, 77, 58, 145, 108, 87, 289, 93, 67, 443, 254, 460, 292, 76, 350, 300, 447, 86, 397, 124, 284, 808, 128, 335, 136 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..5000

EXAMPLE

a(1) = 2 because prime(1)=2 divides (prime(2)+prime(3))/2 = (3+5)/2 = 4.

MAPLE

a:= proc(n) local m, pn; pn:= ithprime(n);

      for m from n+1 while not irem((ithprime(m)+ithprime(m+1))/2, pn)=0

      do od; m

    end:

seq(a(n), n=1..80);  # Alois P. Heinz, Mar 02 2011

MATHEMATICA

leastM[n_]:=Module[{m=1}, While[!Divisible[(Prime[m]+Prime[m+1])/2, n], m++]; m]; leastM/@Prime[Range[60]] (* Harvey P. Dale, Mar 04 2011 *)

CROSSREFS

Cf. A000040, A024675.

Sequence in context: A281645 A351853 A224211 * A179221 A350119 A103964

Adjacent sequences:  A187023 A187024 A187025 * A187027 A187028 A187029

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Mar 02 2011

STATUS

approved

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Last modified October 2 23:51 EDT 2022. Contains 357230 sequences. (Running on oeis4.)