A063425 Unattainable numbers: integers not expressible as k + product of nonzero digits of k (A063114).

1, 3, 5, 7, 9, 13, 15, 17, 19, 21, 25, 27, 30, 31, 36, 37, 39, 40, 43, 48, 49, 51, 52, 53, 57, 59, 61, 63, 64, 69, 71, 72, 73, 76, 79, 82, 83, 84, 87, 90, 91, 93, 96, 97, 103, 105, 113, 115, 117, 119, 121, 127, 131, 136, 137, 139, 148, 149, 151, 153, 157, 159, 163, 164

Offset: 1

Author

Robert G. Wilson v, Aug 09 2001

Keywords

• base
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Paul A. Loomis, An Interesting Family of Iterated Sequences.
• Paul A. Loomis, An Introduction to Digit Product Sequences, J. Rec. Math., 32 (2003-2004), 147-151.
• Paul A. Loomis, An Introduction to Digit Product Sequences, J. Rec. Math., 32 (2003-2004), 147-151. [Annotated archived copy]
• Index entries for Colombian or self numbers and related sequences

Crossrefs

Cf. A063114, A096347, A063425, A096922, A096923, A096924, A096925, A096926, A096927, A096928, A096929, A096930, A096931.

Programs

Mathematica

f[n_] := Block[{s = Sort[ IntegerDigits[n]]}, While[ s[[1]] == 0, s = Drop[s, 1]]; n + Times @@ s]; t = Table[0, {200}]; Do[ a = f[n]; If[a < 200, t[[a]]++ ], {n, 200}]; Select[ Range[ 200], t[[ # ]] == 0 &] (* Robert G. Wilson v, Jul 16 2004 *)