A066027 Numbers k such that the sum of digits of k minus the product of digits of k is prime.
20, 30, 50, 70, 101, 102, 104, 106, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 131, 140, 141, 151, 160, 161, 171, 181, 191, 200, 201, 203, 205, 209, 210, 211, 230, 250, 290, 300, 302, 304, 308, 311, 320, 340, 380, 401, 403, 407, 409, 410
Offset: 1
Examples
a(11)=112 because 1 + 1 + 2 = 4, 2*1*1 = 2, and 4 - 2 = 2, which is prime. [corrected by _Harry J. Smith_, Nov 07 2009]
Links
- Harry J. Smith, Table of n, a(n) for n = 1..1000
Programs
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PARI
isok(k) = {my(d=digits(k)); isprime(vecsum(d) - vecprod(d))} \\ Harry J. Smith, Nov 07 2009