A053543 Distance to closest prime in sequence of composites.

1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 3, 2, 1, 1, 1, 2, 3, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 3, 2, 1, 1, 2, 3, 2, 1, 1, 1, 2, 3, 2, 1, 1, 2, 1, 1, 1, 2, 3, 2, 1, 1, 2, 1, 1, 2, 3, 2, 1, 1, 2, 3, 4, 3, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 1, 1, 2, 1, 1, 2, 3, 2, 1, 1, 1

Offset

1,4

Links

Table of n, a(n) for n=1..105.

Formula

Beginning at 2, list consecutive numbers. Measure distance of each composite to nearest prime.

Example

Fourth composite number is 9; distance to nearest prime, 7 or 11, is 2, so a(4) = 2.

Mathematica

Min[NextPrime[#]-#, #-NextPrime[#, -1]]&/@Select[Range[140], CompositeQ] (* Harvey P. Dale, Aug 31 2015 *)

Crossrefs

Sequence in context: A161100 A342007 A341997 * A161099 A118663 A205119

Adjacent sequences: A053540 A053541 A053542 * A053544 A053545 A053546

Keyword

easy,nonn

Author

Enoch Haga, Jan 16 2000

Status

approved