A105692 Minimal a(n)>0, not appeared previously, such that p(n)*p(n+1)+a(n) is prime.

1, 2, 6, 12, 8, 18, 14, 20, 10, 30, 4, 26, 24, 32, 40, 36, 38, 42, 44, 48, 16, 50, 46, 56, 54, 60, 62, 68, 74, 72, 66, 34, 78, 96, 114, 82, 52, 108, 58, 84, 80, 102, 110, 92, 90, 28, 70, 86, 98, 122, 76, 120, 116, 94, 88, 22, 138, 100, 132, 104, 128, 156, 126, 158, 146, 144

Offset

1,2

Comments

1 and permutation(?) of even integers. Cf. A074928

Links

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

Maple

N:= 200: # for terms before the first term > N
R:= 1: Cands:= 2*[$1..N/2]:
q:= 3:
for nC from nops(Cands) to 1 by -1 do
  p:= q; q:= nextprime(q); s:= p*q;
  found:= false;
  for i from 1 to nC do
    if isprime(s+Cands[i]) then
      found:= true;
      R:= R, Cands[i];
      Cands:= subsop(i=NULL, Cands);
      break
    fi
  od;
  if not found then break fi;
od:
[R]; # Robert Israel, Jun 05 2026

Crossrefs

Cf. A074928.

Sequence in context: A113540 A111658 A341664 * A107647 A210842 A392536

Adjacent sequences: A105689 A105690 A105691 * A105693 A105694 A105695

Keyword

nonn

Author

Zak Seidov, Apr 17 2005

Status

approved