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A256889 Numbers n such that the decimal expansions of both n and n^2 have 1 as smallest digit and 5 as largest digit. 20
115, 1115, 1235, 3515, 11115, 12335, 12415, 33515, 35415, 123335, 123512, 124235, 145415, 152132, 231115, 235211, 333515, 1114115, 1155211, 1233335, 1531115, 1534312, 2311115, 3333515, 11114115, 11141115, 11145511, 12333335, 12342335, 15334312, 15531115 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n can only begin with 1, 2 or 3 and n mod 10 can only equal 1, 2 or 5. - Robert G. Wilson v, Apr 13 2015

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..2000 (n = 1..75 from Robert G. Wilson v).

MATHEMATICA

fQ[n_] := Block[{c = DigitCount@ n}, And[Plus @@ Take[c, {6, 10}] == 0, c[[1]] > 0, c[[5]] > 0]]; Select[Range@ 100000, fQ@ # && fQ[#^2] &] (* Michael De Vlieger, Apr 12 2015 *)

fQ[n_] := Block[{id1 = Union@ IntegerDigits[ n], id2 = Union@ IntegerDigits[ n^2]}, Min[id1] == Min[id2] == 1 && Max[id1] == Max[id2] == 5]; k = 1; lst = {}; While[k < 10^7, If[ fQ@ k, AppendTo[lst, k]]; k++; If[ fQ@ k, AppendTo[lst, k]]; k += 3; If[ fQ@ k, AppendTo[lst, k]]; k += 6]; lst (* Robert G. Wilson v, Apr 13 2015 *)

PROG

(PARI) is(n) = vecmin(digits(n))==1 && vecmin(digits(n^2))==1 && vecmax(digits(n))==5 && vecmax(digits(n^2))==5

CROSSREFS

Cf. A256630, A256631, A256633, A256634, A256708, A256709.

Sequence in context: A218324 A258673 A287430 * A256354 A005466 A279451

Adjacent sequences:  A256886 A256887 A256888 * A256890 A256891 A256892

KEYWORD

base,nonn

AUTHOR

Felix Fröhlich, Apr 12 2015

STATUS

approved

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Last modified June 21 03:05 EDT 2021. Contains 345351 sequences. (Running on oeis4.)