login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A278021 Numbers n such that n - lambda(n) is prime, where lambda = A002322. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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.

LINKS

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

Wikipedia, Carmichael function

FORMULA

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

EXAMPLE

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

MAPLE

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

CROSSREFS

Cf. A002322, A005384, A010051, A277127.

Contains A001248.  Contained in union of A001248 and A024556.

Sequence in context: A109641 A134675 A050530 * A102084 A193315 A030664

Adjacent sequences:  A278018 A278019 A278020 * A278022 A278023 A278024

KEYWORD

nonn

AUTHOR

Robert Israel, Nov 08 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 26 16:52 EDT 2020. Contains 334627 sequences. (Running on oeis4.)