A278021 Numbers n such that n - lambda(n) is prime, where lambda = A002322.

4, 9, 15, 25, 33, 35, 49, 65, 69, 77, 87, 91, 95, 115, 119, 121, 123, 143, 159, 169, 185, 187, 215, 221, 247, 249, 255, 259, 267, 287, 289, 295, 299, 319, 323, 329, 339, 341, 361, 365, 377, 393, 395, 407, 413, 415, 427, 437, 455, 473, 485, 511, 515, 519

Offset: 1

Author

Robert Israel, Nov 08 2016

Keywords

• nonn

Comments

All terms are composite.

4 is the only even term.

For odd primes p, 3*p is a term iff p is in A005384.

Examples

			25-lambda(25) = 25-20 = 5 is prime so 25 is in the sequence.
		

Links

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

Crossrefs

Cf. A002322, A005384, A010051, A277127.

Contains A001248. Contained in union of A001248 and A024556.

Programs

Maple

select(t -> isprime(t - numtheory:-lambda(t)), [$1..10000]);

Formula

A010051(n - A002322(n)) = 1.