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URL: https://oeis.org/A269099

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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.
1
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
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 19 2016
STATUS
approved