Concatenate cell values for duplicate numbers

Here is a formula solution using several helper columns:
Enter in C2 and fill down and across to column E

Formula:

=IF(COUNTIF($A$2:$A2,$A2)=COUNTIF($A$2:$A$19,$A2),"",B3)

Enter in F2 and fill down

Formula:

=IF(C2="","",A2)

Enter in G2 and fill down to enter a , between the values concatenated.

Formula:

=SUBSTITUTE(TRIM(IF(C2="","",B2&" "&C2&" "&D2&" "&E2))," ",", ")

Enter in I2 and fill across and down to get the unique P/N values with the associated H-D#s

Formula:

=IFERROR(INDEX(F$2:F$19,MATCH(1,INDEX((COUNTIF($I$1:I1,$F$2:$F$19)=0)*($F$2:$F$19<>""),0),0)),"")