A038558 Smallest number with derivative n.

0, 2, 4, 5, 8, 9, 11, 10, 16, 17, 19, 18, 23, 22, 20, 21, 32, 33, 35, 34, 39, 38, 36, 37, 47, 46, 44, 45, 40, 41, 43, 42, 64, 65, 67, 66, 71, 70, 68, 69, 79, 78, 76, 77, 72, 73, 75, 74, 95, 94, 92, 93, 88, 89, 91, 90, 80, 81, 83, 82, 87, 86, 84, 85, 128, 129, 131, 130, 135, 134

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• easy

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A038554-A038556.

Programs

Haskell

import Data.List (elemIndex)
import Data.Maybe (fromJust)
a038558 = fromJust . (`elemIndex` a038554_list)
-- Reinhard Zumkeller, Mar 06 2013

Mathematica

dtn[ L_ ] := Fold[ 2#1+#2&, 0, L ]; h[ n_ ] := dtn[ {1}~Join~Table[ Mod[ 1+Apply[ Plus, Take[ IntegerDigits[ n, 2 ], k ] ], 2 ], {k, 1, Length[ IntegerDigits[ n, 2 ] ]} ] ]; Table[ h[ n ], {n, 100} ]

Extensions

More terms from Erich Friedman

a(0)=0 added and offset adjusted by Reinhard Zumkeller, Mar 06 2013