A338974 a(n) is the least prime p such that a(n-1) + p is divisible by a(n-2); a(0)=3, a(1)=5.

3, 5, 7, 3, 11, 7, 37, 5, 439, 11, 7013, 5, 42073, 2, 42071, 3, 168281, 7, 673117, 3, 21539741, 7, 86158957, 11, 344635817, 2, 1723179083, 3, 6892716329, 7, 165425191889, 29, 7278708443087, 19, 43672250658503, 71, 2183612532925079, 829, 183423452765705807, 11, 13573335504662229707, 7

Offset

0,1

Links

Robert Israel, Table of n, a(n) for n = 0..777

Example

a(2) = 7 is the first prime p such that 5+p is divisible by 3.
a(3) = 3 is the first prime p such that 7+p is divisible by 5.
a(4) = 11 is the first prime p such that 3+p is divisible by 7.

Maple

q:= 3: p:= 5: R:= 3, 5:
for i from 2 to 50 do
  t:= (-p) mod q;
  while not isprime(t) do t:= t+q od;
  q:= p; p:= t; R:= R, p;
od:
R;

Crossrefs

Sequence in context: A121573 A196407 A156030 * A255562 A130140 A051417

Adjacent sequences: A338971 A338972 A338973 * A338975 A338976 A338977

Keyword

nonn,look

Author

Robert Israel, Dec 18 2020

Status

approved