Columnn number gwak

Hello,

I've file with 42847 tab sep columns. For demo purpose I'm going to put 6 columns.
Input data (6 columns)

ABCA7   INDO    0.0316847       LARS    0.0400374       ADCK4
CD33    INDO    0.0266461       LARS    0.0970214       ADCK4
TREM2   INDO    0.0179237       LARS    0.0998961       ADCK4
ABCA7   INDO    0.0316847       LARS    0.0400374       ADCK4
CR1     INDO    0.0151277       LARS    0.0378186       ADCK4
PTK2B   INDO    0.0240611       LARS    0.0438327       ADCK4

cut -f -6  test_input_data.txt  | grep "CR1"  |  gawk -v OFS='\t' '{ for (i;i<=NF ;i++)  { if ( $i ~ /LARS/ ) {print i} } }'

I'm cutting 6 columns from input file so I can grep CR1.
Next I'm interested to get column number of LARS in the grepped output.

I get output as

4

1)
A blank line and 4. It looks OK, but I don't know why I get a blank line.

I got code from link

Try for (i=1; ...