A342609 Positive integers that cannot be written in the form k - gpf(k) +- 1 for some integer k, where gpf(k) is the greatest prime factor of k.

17, 49, 161, 197, 199, 209, 251, 391, 419, 449, 649, 685, 769, 799, 883, 967, 1057, 1189, 1249, 1301, 1457, 1481, 1681, 1793, 1937, 1979, 2001, 2029, 2089, 2177, 2209, 2311, 2377, 2379, 2419, 2431, 2449, 2549, 2551, 2575, 2591, 2705, 2729, 2899, 3041, 3073

Offset: 1

Author

Christian Bagshaw, Mar 16 2021

Keywords

• nonn

Links

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

Crossrefs

Cf. A006530, A076563.

Programs

Maple

f:= proc(n) local g;
  g:= max(numtheory:-factorset(n));
  n-g+1,n-g-1
end proc:
sort(convert({$1..5000} minus map(f, {$1..10001}),list)); # Robert Israel, Apr 12 2021