A269099 Numbers n with the property that if there is a number j with prime(n+i) + prime(n-i) = j for some i, then there are least two choices for i that give this value of j.

5, 10, 13, 16, 20, 25, 31, 32, 33, 37, 40, 41, 43, 44, 47, 51, 54, 63, 64, 70, 71, 72, 73, 74, 75, 76, 78, 79, 80, 84, 85, 86, 87, 93, 98, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 115, 126, 129, 130, 132, 133, 134, 135, 136, 137

Offset

1,1

Links

Michel Lagneau, Table of n, a(n) for n = 1..5000

Example

5 is a member because we have:
prime(5 + 3) + prime(5 - 3) = 19 + 3 = 22;
prime(5 + 2) + prime(5 - 2) = 17 + 5 = 22.
10 is a member because we have:
prime(10 + 2) + prime(10 - 2) = 19 + 37 = 56;
prime(10 + 3) + prime(10 - 3) = 17 + 41 = 58;
prime(10 + 4) + prime(10 - 4) = 13 + 43 = 56;
prime(10 + 5) + prime(10 - 5) = 11 + 47 = 58;
prime(10 + 7) + prime(10 - 7) = 5 + 59 = 64;
prime(10 + 8) + prime(10 - 8) = 3 + 61 = 64;
and all the sums 56, 58 and 64 appear twice.

Maple

for n from 1 to 200 do:
  lst:={}:W:=array(1..n-1):cr:=0:
    for m from n-1 by -1 to 1 do:
      q:=ithprime(n-m)+ithprime(n+m):lst:=lst union {q}:W[m]:=q:cr:=cr+1:
    od:c:=0:
for k from 1 to cr do:
if W[k]=2*ithprime(n) then c:=c+1:
  else fi:
od:
if c>1 then
      printf(`%d, `, n):
      else fi:
  od :

Crossrefs

Cf. A269043.

Sequence in context: A092604 A313380 A313381 * A313382 A313383 A313384

Adjacent sequences: A269096 A269097 A269098 * A269100 A269101 A269102

Keyword

nonn

Author

Michel Lagneau, Feb 19 2016

Status

approved