A226319 a(n) is the smallest odd k > 1 such that k is a Niven number at least in all the bases from 1 to n.

3, 21, 21, 21, 675, 4725, 4725, 98175, 140175, 543375, 543375, 23186625, 35026425, 139264125, 139264125, 608679225, 11553990525, 87662479905, 87662479905, 343947649815, 2383529269275, 4005262262925, 4005262262925

Offset: 1

Author

Giovanni Resta, Jun 03 2013

Keywords

• nonn
• base

Examples

			a(4) = 21 because 21 is the smallest odd k > 1 which is Niven in bases 1 (trivial), 2, 3, and 4, being equal to (10101)_2, (210)_3 and (111)_4.
		

Crossrefs

Cf. A005349, A226169, A226320, A225427 (Niven in bases 1,...,n but not in base n+1).

Programs

Mathematica

a[n_] := Block[{k=3}, n > 1 &&  While[Max@ Mod[k, Total /@ IntegerDigits[k, Range[2, n]]] > 0, k += 2]; k]; Array[a,9]