A361215 Intersection of A361073 and 2 * A361611.

8, 20, 50, 1406, 1516, 1558, 1868, 1898, 1948, 1978, 1986, 5862, 5972, 6014, 7122, 7966, 7996, 8270, 8348, 8366, 8548, 8618, 21092, 31804, 31822, 32158, 33092, 33162, 33316, 33414, 37124, 37190, 37292, 37394, 39164, 39214, 39316, 39346, 39484, 39562, 39604, 39622, 39692, 39794, 45044, 45244

Offset

1,1

Comments

If A361073(j) = 2*A361611(k) then x = 2*A361611(k+1) has the property that x, x - A361073(j) and x + A361073(j) are triprimes, so x >= A361073(j+1), with equality if and only if A361073(j+1) is even.

Links

Robert Israel, Table of n, a(n) for n = 1..2900

Example

a(4) = 1406 is a term because 1406 = A361073(20) = 2*A361611(17).

Maple

A:= {8}: lasta:= 8:
for i from 2 to 1000 do
  for x from lasta+8 do
    if numtheory:-bigomega(x) = 3 and numtheory:-bigomega(x-lasta) = 3 and numtheory:-bigomega(x+lasta) = 3 then
       A:= A union {x}; lasta:= x; break
    fi
od od:
R:= {8}: lastb:= 4:
while 2*lastb < lasta do
for x from lastb+4 do
  if numtheory:-bigomega(x) = 2 and numtheory:-bigomega(x-lastb) = 2 and numtheory:-bigomega(x+lastb) = 2 then
     if member(2*x, A) then R:= R union {2*x} fi;
     lastb:= x; break
  fi
od od:
sort(convert(R, list));

Crossrefs

Cf. A361073, A361611.

Sequence in context: A169878 A107816 A361073 * A205219 A232401 A036835

Adjacent sequences: A361212 A361213 A361214 * A361216 A361217 A361218

Keyword

nonn

Author

Zak Seidov and Robert Israel, Apr 09 2023

Status

approved