A050627 Product of digits of n is a nonzero single-digit square.

1, 4, 9, 11, 14, 19, 22, 33, 41, 91, 111, 114, 119, 122, 133, 141, 191, 212, 221, 313, 331, 411, 911, 1111, 1114, 1119, 1122, 1133, 1141, 1191, 1212, 1221, 1313, 1331, 1411, 1911, 2112, 2121, 2211, 3113, 3131, 3311, 4111, 9111, 11111, 11114, 11119, 11122, 11133

Offset: 1

Author

Patrick De Geest, Jun 15 1999

Keywords

• nonn
• base

Comments

I.e., the product of digits is 1, 4, or 9. - Franklin T. Adams-Watters, Sep 27 2016

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007954, A028845, A028839, A002275 (a subsequence).

Programs

Maple

f:= proc(d) local R,i;
  R:= [1$d],seq([1$i,4,1$(d-1-i)],i=0..d-1),seq([1$i,9,1$(d-1-i)],i=0..d-1);
  if d >= 2 then R:= R, op(combinat:-permute([1$(d-2),2,2])), op(combinat:-permute([1$(d-2),3,3])) fi;
  op(sort(map(proc(L) local i; add(L[i]*10^(i-1),i=1..d) end proc, [R])))
end proc:
map(f, [$1..6]); # Robert Israel, Apr 09 2025

Mathematica

Select[Range[12000],MemberQ[{1,4,9},Times@@IntegerDigits[#]]&] (* Harvey P. Dale, Jan 22 2016 *)