A187026 Least m such that prime(n) divides (prime(m) + prime(m+1))/2.

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

Offset: 1

Author

Vladimir Shevelev, Mar 02 2011

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A000040, A024675.

Programs

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 *)