A131848 Least nonnegative number which when added to the n-th semiprime gives a multiple of n.

0, 0, 0, 2, 1, 3, 0, 2, 2, 4, 0, 2, 4, 4, 6, 2, 2, 3, 2, 3, 5, 4, 4, 3, 1, 1, 26, 27, 1, 3, 2, 3, 5, 7, 34, 33, 33, 34, 37, 39, 1, 3, 0, 43, 1, 43, 46, 1, 2, 4, 49, 50, 0, 1, 54, 55, 51, 54, 53, 55, 57, 54, 51, 54, 57, 59, 62, 63, 63, 66, 69, 71, 1, 3, 4, 2, 73, 75, 69, 71

Offset

1,4

Comments

This is to semiprimes A001358 as A068901 is to primes A000040.

Links

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

Formula

a(n) = MIN{k=>0 such that n|(k+A001358(n))}.

Example

a(1) = 0 because 1 | (0+semiprime(1)=4).
a(6) = 3 because 6 | (3+semiprime(3)=3+15=18).
a(25) = 1 because 25 | (1+semiprime(25)=1+74=75).

Mathematica

lnn[{s_, n_}]:=If[Divisible[s, n], 0, n-Mod[s, n]]; lnn/@Module[{sp=Select[ Range[ 300], PrimeOmega[#] ==2&], len}, len=Length[sp]; Thread[{sp, Range[len]}]] (* Harvey P. Dale, Mar 23 2013 *)

Crossrefs

Cf. A000040, A001358, A068901.

Sequence in context: A091829 A194188 A104512 * A287873 A035157 A318995

Adjacent sequences: A131845 A131846 A131847 * A131849 A131850 A131851

Keyword

easy,nonn

Author

Jonathan Vos Post, Oct 04 2007

Extensions

More terms from R. J. Mathar, Jan 15 2008

Status

approved