The following are countries that Fountain supports for IBAN validation:
AL: 28, // Albania
AD: 24, // Andorra
AT: 20, // Austria
AZ: 28, // Azerbaijan
BH: 22, // Bahrain
BY: 28, // Belarus
BE: 16, // Belgium
BA: 20, // Bosnia and Herzegovina
BR: 29, // Brazil
BG: 22, // Bulgaria
CR: 22, // Costa Rica
HR: 21, // Croatia
CY: 28, // Cyprus
CZ: 24, // Czech Republic
DK: 18, // Denmark
DO: 28, // Dominican Republic
EG: 29, // Egypt
SV: 28, // El Salvador
EE: 20, // Estonia
FO: 18, // Faroe Islands
FI: 18, // Finland
FR: 27, // France
GE: 22, // Georgia
DE: 22, // Germany
GI: 23, // Gibraltar
GR: 27, // Greece
GL: 18, // Greenland
GT: 28, // Guatemala
VA: 22, // Holy See (the)
HU: 28, // Hungary
IS: 26, // Iceland
IQ: 23, // Iraq
IE: 22, // Ireland
IL: 23, // Israel
IT: 27, // Italy
JO: 30, // Jordan
KZ: 20, // Kazakhstan
XK: 20, // Kosovo
KW: 30, // Kuwait
LV: 21, // Latvia
LB: 28, // Lebanon
LY: 25, // Libya
LI: 21, // Liechtenstein
LT: 20, // Lithuania
LU: 20, // Luxembourg
MT: 31, // Malta
MR: 27, // Mauritania
MU: 30, // Mauritius
MD: 24, // Moldova
MC: 27, // Monaco
ME: 22, // Montenegro
NL: 18, // Netherlands
MK: 19, // North Macedonia
NO: 15, // Norway
PK: 24, // Pakistan
PS: 29, // Palestine
PL: 28, // Poland
PT: 25, // Portugal
QA: 29, // Qatar
RO: 24, // Romania
LC: 32, // Saint Lucia
SM: 27, // San Marino
ST: 25, // Sao Tome and Principe
SA: 24, // Saudi Arabia
RS: 22, // Serbia
SC: 31, // Seychelles
SK: 24, // Slovak Republic
SI: 19, // Slovenia
ES: 24, // Spain
SD: 18, // Sudan
SE: 24, // Sweden
CH: 21, // Switzerland
TL: 23, // Timor-Leste
TN: 24, // Tunisia
TR: 26, // Turkey
UA: 29, // Ukraine
AE: 23, // United Arab Emirates
GB: 22, // United Kingdom
VG: 24, // Virgin Islands, British