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 A136975 Numbers k such that k and k^2 use only the digits 1, 2, 3, 5 and 7. 1
 1, 5, 11, 15, 35, 111, 115, 235, 335, 715, 1235, 2715, 3335, 3511, 3515, 3711, 12335, 27115, 33335, 33515, 35711, 37115, 72335, 75711, 111235, 123335, 132335, 177515, 333335, 333515, 357115, 572115, 575515, 577515, 723335, 757115, 1233335, 1312335, 1323335, 3333335, 3333515, 3512511, 5227115, 5772115, 7233335, 11212115, 11277115, 11735515 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Generated with DrScheme. Sequence is infinite; e.g., it contains 3...35 = (10^n-1)/3 + 2 for all n. - Robert Israel, Nov 24 2015 a(n) mod 100 can be only 11, 15 or 35 for n > 2. So if a(n) is a prime number, a(n) mod 100 = 11 for n > 2. Initial prime values of a(n) are 11, 3511 and 12375511 for n > 2. - Altug Alkan, Nov 25 2015 LINKS Jonathan Wellons, Table of n, a(n) for n = 1..330 J. Wellons, Tables of Shared Digits EXAMPLE 757313127132715^2 = 573523172527531752317223271225. MAPLE f2:= proc(n) local L; convert(convert(n^2, base, 10), set) intersect {4, 6, 8, 9, 0} = {} end proc: S:= {0}: A:= {}: for d from 1 to 8 do   S:={seq(seq(10*s+j, j=[1, 2, 3, 5, 7]), s=S)};   A:= select(f2, S) union A; od: sort(convert(A, list)); # Robert Israel, Nov 24 2015, corrected Sep 03 2020 MATHEMATICA w = {1, 2, 3, 5, 7}; Select[Range[1, 10^7, 2], Union[IntegerDigits@ #, IntegerDigits[#^2], w] == w &] (* Michael De Vlieger, Nov 25 2015 *) CROSSREFS Cf. A001742, A034905. Sequence in context: A034905 A031153 A136976 * A136973 A276037 A221743 Adjacent sequences:  A136972 A136973 A136974 * A136976 A136977 A136978 KEYWORD base,nonn AUTHOR Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008 STATUS approved

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Last modified January 19 06:18 EST 2022. Contains 350464 sequences. (Running on oeis4.)