A075430 Primes with a squarefree neighbor.

2, 3, 5, 7, 11, 13, 23, 29, 31, 37, 41, 43, 47, 59, 61, 67, 71, 73, 79, 83, 101, 103, 107, 109, 113, 131, 137, 139, 157, 167, 173, 179, 181, 191, 193, 211, 223, 227, 229, 239, 257, 263, 277, 281, 283, 311, 313, 317, 331, 347, 353, 359, 367, 373, 383, 389, 397

Offset

1,1

Comments

Union of A039787 and A049097; complement of A075432 in A000040.

Links

Enrique Pérez Herrero, Table of n, a(n) for n = 1..1000

Example

a(3) = 5 because 6 (the number above) is squarefree.
a(13) = 47 because 46 (the number below) is squarefree.
53 is not in the sequence because both 52 and 54 have squares among their divisors.

Prog

(Sage) def is_A075430(n): return is_prime(n) and (is_squarefree(n-1) or is_squarefree(n+1)) # D. S. McNeil, Jan 16 2011
(PARI) isok(p) = isprime(p) && (issquarefree(p-1) || issquarefree(p+1)); \\ Michel Marcus, Feb 20 2023

Crossrefs

Cf. A005117, A000040.

Sequence in context: A357659 A334041 A181172 * A095080 A350179 A229289

Adjacent sequences: A075427 A075428 A075429 * A075431 A075432 A075433

Keyword

nonn

Author

Reinhard Zumkeller, Sep 15 2002

Status

approved