A341237 a(k) is the number of pairs of consecutive primes (p,q) such that (2*k-q,2*k-p) is also a pair of consecutive primes.

0, 0, 0, 1, 2, 1, 0, 2, 3, 0, 2, 5, 0, 0, 5, 0, 2, 5, 0, 0, 3, 0, 2, 6, 0, 1, 6, 0, 0, 9, 0, 2, 4, 1, 0, 4, 0, 4, 7, 0, 2, 9, 0, 0, 13, 0, 0, 2, 2, 1, 8, 0, 4, 6, 2, 5, 14, 0, 0, 17, 0, 0, 10, 1, 0, 8, 0, 2, 7, 2, 4, 11, 0, 0, 14, 1, 2, 6, 0, 2, 7, 0, 0, 12, 0, 1, 8, 0, 0, 14, 0, 4, 9, 2, 2, 6, 2

Offset

1,5

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(9) = 3 because (5,7), (7,11) and (11,13) are pairs of consecutive primes (p,q) with (18-q,18-p) = (11,13), (7,11) and (5,7) also consecutive primes.

Maple

f:= proc(n) local p, q, count;
  q:= 2: count:= 0:
  while q < 2*n -2 do
    p:= q; q:= nextprime(q);
    if isprime(2*n-p) and prevprime(2*n-p)=2*n-q then count:= count+1 fi;
  od;
  count
end proc:
map(f, [$1..100]);

Crossrefs

Cf. A002372.

Sequence in context: A144027 A019591 A353984 * A091967 A031135 A037181

Adjacent sequences: A341234 A341235 A341236 * A341238 A341239 A341240

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Feb 07 2021

Status

approved