A193551 Smallest number with n as multiplicative projection.

1, 2, 3, 4, 5, 6, 7, 16, 27, 10, 11, 12, 13, 14, 15, 256, 17, 24, 19, 20, 21, 22, 23, 36, 3125, 26, 19683, 28, 29, 30, 31, 65536, 33, 34, 35, 72, 37, 38, 39, 80, 41, 42, 43, 44, 135, 46, 47, 144, 823543, 160, 51, 52, 53, 216, 55, 112, 57, 58, 59, 60, 61, 62

Offset: 1

Author

Reinhard Zumkeller, Aug 27 2011

Keywords

• nonn

Comments

A000026(a(n)) = n and A000026(m) <> n for m < a(n);

a(p^k) = p^(p^(k-1)), p prime, k > 0; the sequence is not multiplicative, but for coprime odd numbers u, v: a(u*v) = a(u) * a(v);

A078779 gives fixed points: a(A078779(n)) = A078779(n).

Programs

Haskell

import Data.List (elemIndex, findIndices)
import Data.Maybe (fromJust)
a193551 n = (fromJust $ elemIndex n a000026_list) + 1