Dutch RSIN

What it covers

Returns a valid Dutch RSIN (Rechtspersonen en Samenwerkingsverbanden Informatienummer) with a correct elfproef check. The RSIN is non-semantic. Set `invalid=true` for an RSIN with a deliberately wrong check digit, or `edge=true` for valid edge-case numbers.

How it’s calculated

The RSIN's final digit is a weighted-sum modulo-11 check digit (the Dutch "elfproef"), identical to the BSN scheme, taken as the raw remainder of the weighted sum of the eight leading digits.

Payload digits: [1,2,3,4,5,6,7,8], weights [9,8,7,6,5,4,3,2].
Products: 9*1=9, 8*2=16, 7*3=21, 6*4=24, 5*5=25, 4*6=24, 3*7=21, 2*8=16.
Sum = 9+16+21+24+25+24+21+16 = 156.
156 mod 11: 11*14 = 154, remainder = 156 - 154 = 2.
Style 'remainder' -> raw check = 2. Overflow 'invalid': 2 is neither 10 nor 11, so it stands.
Check digit = 2.

Edge cases

• When the weighted sum of the eight leading digits is congruent to 10 (mod 11), no single digit satisfies the elfproef, so that prefix is 'dead' — the generator returns undefined and redraws (generateRsinDigits loops until a valid prefix is found).
• The common-shape generator draws the first digit in the range 1..9 (no leading zero); leading-zero forms are reserved for the edge generator.
• The check digit is the raw remainder, not the 11-complement — this matches the BSN scheme, because the full elfproef weight on the 9th (check) digit is -1.

Gotchas

• RSIN uses the same elfproef (weights 9,8,7,6,5,4,3,2 and the -1 on the 9th digit) as the 9-digit BSN, so an RSIN passes the BSN check too; they share number space but are semantically different (RSIN identifies legal entities/partnerships, BSN identifies natural persons).
• Because the ninth-digit weight is -1, the check equals the plain weighted sum of the first eight digits mod 11 (remainder style) — do NOT apply an 11-complement, which would give the wrong digit.
• Digit strings must never round-trip through Number: leading zeros are significant, so arithmetic is done on the digit array via toDigits.