

A117369


a(n) = smallest prime which is > smallest prime dividing n and is coprime to n.


1



2, 3, 5, 3, 7, 5, 11, 3, 5, 3, 13, 5, 17, 3, 7, 3, 19, 5, 23, 3, 5, 3, 29, 5, 7, 3, 5, 3, 31, 7, 37, 3, 5, 3, 11, 5, 41, 3, 5, 3, 43, 5, 47, 3, 7, 3, 53, 5, 11, 3, 5, 3, 59, 5, 7, 3, 5, 3, 61, 7, 67, 3, 5, 3, 7, 5, 71, 3, 5, 3, 73, 5, 79, 3, 7
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OFFSET

1,1


LINKS

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


EXAMPLE

a(6) = 5 because 5 is the smallest prime which is both greater than the smallest prime dividing 6, which is 2 and is coprime to 6.


MATHEMATICA

a[1] := 2; a[n_] := Module[{}, k = PrimePi[FactorInteger[n][[1, 1]]]; k++; While[Not[GCD[Prime[k], n] == 1 ], k++ ]; Prime[k]]; Table[a[i], {i, 1, 80}] (* Stefan Steinerberger and Patrick Hanslmaier, Jun 03 2007 *)
spdn[n_]:=Module[{s=FactorInteger[n][[1, 1]], p}, p=NextPrime[s]; While[ !CoprimeQ[ p, n], p=NextPrime[p]]; p]; Array[spdn, 80] (* Harvey P. Dale, Feb 18 2018 *)


CROSSREFS

Cf. A079068, A117367.
Sequence in context: A080184 A052248 A092386 * A117366 A073482 A318411
Adjacent sequences: A117366 A117367 A117368 * A117370 A117371 A117372


KEYWORD

nonn


AUTHOR

Leroy Quet, Mar 10 2006


EXTENSIONS

More terms from Stefan Steinerberger and Patrick Hanslmaier, Jun 03 2007


STATUS

approved



