A366217 a(n) is the least semiprime > a(n-2) + a(n-1), with a(1) = 4 and a(2) = 6.

4, 6, 14, 21, 38, 62, 106, 169, 278, 451, 731, 1186, 1919, 3106, 5027, 8135, 13165, 21302, 34473, 55779, 90253, 146035, 236291, 382327, 618622, 1000951, 1619581, 2620538, 4240121, 6860662, 11100785, 17961455, 29062241, 47023697, 76085941, 123109639, 199195583, 322305254, 521500838, 843806099

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..300

Example

a(3) = 14 because 14 = 2*7 is a semiprime, 14 > a(1) + a(2) = 10, and none of 11, 12 and 13 are semiprimes.

Maple

R:= 4, 6: a:= 4: b:= 6:
for count from 3 to 100 do
  for v from a+b+1 do
    if numtheory:-bigomega(v) = 2 then
       R:= R, v; a:= b; b:= v; break
    fi
od od:
R;

Crossrefs

Cf. A001358.

Sequence in context: A310650 A310651 A122555 * A210632 A097271 A126867

Adjacent sequences: A366214 A366215 A366216 * A366218 A366219 A366220

Keyword

nonn

Author

Zak Seidov and Robert Israel, Oct 04 2023

Status

approved