A073784 Number of primes between successive composite numbers.

1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

a(7) = 0 since there are no primes between the 7th and the 8th composites (14 and 15).

Mathematica

Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; Table[ PrimePi[Composite[n + 1]] - PrimePi[Composite[n]], {n, 105}] (* Robert G. Wilson v, Dec 20 2004 *)
Differences[Select[Range[300], CompositeQ]]-1 (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 01 2021 *)

Crossrefs

a(n) = A073783(n) - 1.

a(n) = A002808(n+1) - A002808(n) - 1.

Also first differences of A073425.

Sequence in context: A352573 A285345 A125999 * A320006 A219977 A128130

Adjacent sequences: A073781 A073782 A073783 * A073785 A073786 A073787

Keyword

easy,nonn

Author

Lior Manor, Aug 11 2002

Status

approved