A342408 a(n) is the least prime that begins a string of n consecutive primes such that the sum of each consecutive pair in the string is divisible by 8.

2, 3, 53, 53, 523, 6337, 36947, 36947, 277363, 8177791, 8622017, 8622017, 565337239, 3361495721, 16747915297, 76675792867, 76675792867, 633679985683, 633679985683, 4443195645419, 21685290410821, 205793034752197

Offset

1,1

Links

Table of n, a(n) for n=1..22.

Example

a(4) = 53 because 53, 59, 61, 67 are consecutive primes with 53+59 = 112. 59+61 = 120, 61+67 = 128 all divisible by 8.

Maple

p:= 2: p0:= 2: vmax:= 1: R:= 2: v:= 1;
while vmax < 10 do
  q:= p;
  p:= nextprime(p);
  if q+p mod 8 = 0 then
    v:= v+1;
    if v > vmax then
      vmax:= v; R:= R, p0;
    fi;
  else
    p0:= p; v:= 1;
  fi
od:
R;

Crossrefs

Sequence in context: A192182 A090231 A202701 * A062641 A339920 A344732

Adjacent sequences: A342405 A342406 A342407 * A342409 A342410 A342411

Keyword

nonn,more

Author

J. M. Bergot and Robert Israel, Mar 30 2021

Extensions

a(13)-a(15) from Chai Wah Wu, Mar 31 2021

a(16)-a(19) from Chai Wah Wu, Apr 07 2021

a(20)-a(22) from Martin Ehrenstein, Apr 15 2021

Status

approved