A090369 Smallest divisor of 2n that is > 2, or 0 if no such divisor exists.

0, 4, 3, 4, 5, 3, 7, 4, 3, 4, 11, 3, 13, 4, 3, 4, 17, 3, 19, 4, 3, 4, 23, 3, 5, 4, 3, 4, 29, 3, 31, 4, 3, 4, 5, 3, 37, 4, 3, 4, 41, 3, 43, 4, 3, 4, 47, 3, 7, 4, 3, 4, 53, 3, 5, 4, 3, 4, 59, 3, 61, 4, 3, 4, 5, 3, 67, 4, 3, 4, 71, 3, 73, 4, 3, 4, 7, 3, 79, 4, 3, 4, 83, 3, 5, 4, 3, 4, 89, 3, 7, 4, 3, 4, 5

Offset: 1

Author

Lekraj Beedassy, Nov 27 2003

Keywords

• nonn
• easy

Links

• Remi Eismann, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A090368, A020639, A117078, A117563, A118534.

Programs

Maple

A090369 := proc(n) local lf,i ; lf := numtheory[divisors](2*n) ; for i from 1 to nops(lf) do if op(i,lf) > 2 then RETURN( op(i,lf) ) ; fi ; od ; RETURN(0) ; end : for n from 0 to 100 do printf("%d,",A090369(n)) ; od ; # R. J. Mathar, Jun 02 2006

Mathematica

Join[{0},Table[SelectFirst[Divisors[2n],#>2&],{n,2,120}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 24 2017 *)

Extensions

More terms from Ray Chandler, Dec 02 2003

Edited by N. J. A. Sloane at the suggestion of Rémi Eismann, Sep 15 2007