A053087 - OEIS

A053087

a(n) is the smallest j for which 2^j kara n is defined (see A053405).

0, 1, 3, 2, 5, 4, 5, 3, 7, 6, 5, 7, 6, 8, 7, 4, 9, 8, 7, 8, 9, 6, 9, 8, 9, 7, 9, 10, 8, 10, 9, 5, 11, 10, 9, 10, 8, 10, 11, 9, 10, 11, 7, 11, 10, 11, 9, 11, 10, 11, 12, 8, 11, 10, 12, 11, 9, 12, 11, 12, 10, 12, 11, 6, 13, 12, 11, 12, 10, 12, 11, 12, 13, 9, 12, 11, 13, 12, 10

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OFFSET

1,3

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

EXAMPLE

a(6)=4 because 2^3 kara 6 is undefined, but 16 kara 6 = 3.

PROG

(Haskell)

a053087 n = head [j | j <- [0..], (2 ^ j) `kara` n /= Nothing] where

kara a b = if null ks then Nothing else Just $ head ks

where ks = [c | c <- [1..a], a <= c * b, a > c * (b - 1)]