A096916 Lesser prime factor of n-th product of two distinct primes.

2, 2, 2, 3, 3, 2, 2, 3, 2, 5, 2, 3, 2, 3, 5, 3, 2, 2, 5, 3, 2, 7, 2, 5, 2, 3, 7, 3, 2, 5, 2, 3, 5, 2, 7, 2, 3, 3, 7, 2, 3, 2, 11, 5, 2, 5, 2, 3, 7, 2, 3, 2, 3, 5, 11, 2, 3, 2, 7, 5, 2, 11, 3, 2, 5, 7, 2, 3, 13, 2, 5, 3, 13, 3, 11, 2, 7, 2, 5, 3, 2, 2, 7, 3, 5, 2, 13, 7, 2, 3, 5, 3, 2, 11, 3, 17, 2, 3

Offset

1,1

Comments

a(n)*A070647(n) = A006881(n); a(n) < A070647(n);

a(n) = A020639(A006881(n)).

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1, 1}; f1[n_]:=Min[First/@FactorInteger[n]]; f2[n_]:=Max[First/@FactorInteger[n]]; lst={}; Do[If[f[n], AppendTo[lst, f1[n]]], {n, 0, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Apr 10 2010 *)

Prog

(Haskell)
a096916 = a020639 . a006881 -- Reinhard Zumkeller, Sep 23 2011
(PARI) go(x)=my(v=List()); forprime(p=2, sqrtint(x\1), forprime(q=p+1, x\p, listput(v, [p*q, p]))); apply(v->v[2], vecsort(Vec(v), 1)) \\ Charles R Greathouse IV, Sep 14 2015

Crossrefs

Cf. A084126, A195758.

Sequence in context: A124064 A348470 A317369 * A098014 A059957 A361088

Adjacent sequences: A096913 A096914 A096915 * A096917 A096918 A096919

Keyword

nonn,look

Author

Reinhard Zumkeller, Jul 15 2004

Status

approved