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

%I A050627 #24 Apr 10 2025 15:59:01
%S A050627 1,4,9,11,14,19,22,33,41,91,111,114,119,122,133,141,191,212,221,313,
%T A050627 331,411,911,1111,1114,1119,1122,1133,1141,1191,1212,1221,1313,1331,
%U A050627 1411,1911,2112,2121,2211,3113,3131,3311,4111,9111,11111,11114,11119,11122,11133
%N A050627 Product of digits of n is a nonzero single-digit square.
%C A050627 I.e., the product of digits is 1, 4, or 9. - _Franklin T. Adams-Watters_, Sep 27 2016
%H A050627 Robert Israel, <a href="/A050627/b050627.txt">Table of n, a(n) for n = 1..10000</a>
%p A050627 f:= proc(d) local R,i;
%p A050627   R:= [1$d],seq([1$i,4,1$(d-1-i)],i=0..d-1),seq([1$i,9,1$(d-1-i)],i=0..d-1);
%p A050627   if d >= 2 then R:= R, op(combinat:-permute([1$(d-2),2,2])), op(combinat:-permute([1$(d-2),3,3])) fi;
%p A050627   op(sort(map(proc(L) local i; add(L[i]*10^(i-1),i=1..d) end proc, [R])))
%p A050627 end proc:
%p A050627 map(f, [$1..6]); # _Robert Israel_, Apr 09 2025
%t A050627 Select[Range[12000],MemberQ[{1,4,9},Times@@IntegerDigits[#]]&] (* _Harvey P. Dale_, Jan 22 2016 *)
%Y A050627 Cf. A007954, A028845, A028839, A002275 (a subsequence).
%K A050627 nonn,base
%O A050627 1,2
%A A050627 _Patrick De Geest_, Jun 15 1999