A331619 a(n) is the smallest positive number k such that the decimal expansion of n*2^k contains the string n.

1, 4, 4, 7, 4, 9, 4, 8, 4, 10, 10, 10, 10, 10, 10, 10, 10, 7, 10, 10, 4, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 4, 10, 28, 19, 13, 15, 16, 40, 20, 30, 53, 27, 20, 27, 35, 30, 20, 53, 31, 20, 4, 8, 18, 35, 20, 10, 30, 23, 20

Offset: 0

Author

Rémy Sigrist, Jan 22 2020

Keywords

• nonn
• base

Examples

			  n   a(n)  n*2^a(n)
  --  ----  --------
   0     1         0
   1     4        16
   2     4        32
   3     7       384
   4     4        64
   5     9      2560
   6     4        96
   7     8      1792
   8     4       128
   9    10      9216
  10    10     10240
		

Links

• Rémy Sigrist, PARI program for A331619

Crossrefs

Cf. A030000, A331440.