A050627 - OEIS

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

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OFFSET

1,2

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

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])))