A056141 a(n) = primefloor(n)*primeceiling(n) - previousprime(n)*nextprime(n).

-1, 0, 4, 0, -6, 0, 0, 0, 30, 0, -18, 0, 0, 0, 42, 0, -30, 0, 0, 0, -22, 0, 0, 0, 0, 0, 128, 0, -112, 0, 0, 0, 0, 0, 98, 0, 0, 0, 90, 0, -78, 0, 0, 0, -70, 0, 0, 0, 0, 0, 36, 0, 0, 0, 0, 0, 248, 0, -232, 0, 0, 0, 0, 0, 158, 0, 0, 0, 150, 0, -280, 0, 0, 0, 0, 0, 182

Offset

3,3

Links

Table of n, a(n) for n=3..79.

Formula

a(n) = A007917(n)*A007918(n) - A007917(n-1)*A007918(n+1).

a(n) = A030664(n) - A013638(n).

a(n) = A056140(n) - A056139(n).

a(n) = A056140(n) if n is prime, a(n)=0 otherwise.

Example

a(3)=3*3-2*5=-1, a(4)=3*5-3*5=0

Prog

(PARI) a(n) = if (isprime(n), n^2 - precprime(n-1)*nextprime(n+1), 0); \\ Michel Marcus, Mar 22 2020

Crossrefs

Cf. A056139, A056140.

Cf. A056221 (nonzero terms).

Sequence in context: A308678 A184365 A126813 * A246004 A103688 A125961

Adjacent sequences: A056138 A056139 A056140 * A056142 A056143 A056144

Keyword

easy,sign

Author

Henry Bottomley, Jun 15 2000

Extensions

More terms from Michel Marcus, Mar 22 2020

Status

approved