Code: PU P=100 (k=72=16 (mod 28) )
Formulae:
Number N is divisible by 28 iff 16b+a = -12b+a is divisible by 28
Example:
Number N = 98 76 54 32 08 = 14 20 26 4 8 =
-12( 14 20 26 4)+8 =
-12(-12( 14 20 26+4)+8 =
-12(-12(-12( 14 20+26)+4)+8 =
-12(-12(-12(-12*14+20)+26)+4)+8 =
-12(-12(-12* 20+26)+4)+8 =
-12(-12* 10+4)+8
-12* 24+8 = 0 (mod 28)
is divisible by 28.
Code: PS, PD
P=1000, (k=8). 1008 = 36*28
Formulae:
Number N is divisible by 28 iff -8b+a is divisible by 28
Example:
Number N = 68 940 with base P=1000
-8*68 + 940 = 396 = 14*28+4
Number N isn't divisible by 28
