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 A137110 Numbers k such that k and k^2 use only the digits 2, 5, 6 and 7. 5
 5, 25, 26, 75, 76, 275, 525, 526, 725, 7525, 27525, 72576, 256266, 276725, 725725, 276726675, 756652275 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Generated with DrScheme. If it exists, a(18) > 10^34. - David A. Corneth and Michael S. Branicky, May 25 2021 LINKS Table of n, a(n) for n=1..17. David A. Corneth, PARI program Jonathan Wellons, Tables of Shared Digits EXAMPLE 276726675^2 = 76577652656555625. PROG (Python) def auptod(maxdigits, only="2567"): aset, digset, valid = set(), set(only), set(only) for e in range(1, maxdigits+1): newvalid = set() for tstr in valid: t = int(tstr) if set(str(t**2)) <= digset: aset.add(t) for d in digset: dtstr = d + tstr dt = int(dtstr) remstr = str(dt**2)[-e-1:] if set(remstr) <= digset: newvalid.add(dtstr) valid = newvalid return sorted(aset) print(auptod(16)) # Michael S. Branicky, May 25 2021 (PARI) See PARI-link \\ David A. Corneth, May 25 2021 CROSSREFS Sequence in context: A070381 A136912 A137111 * A036137 A070380 A068574 Adjacent sequences: A137107 A137108 A137109 * A137111 A137112 A137113 KEYWORD base,nonn,more AUTHOR Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008 STATUS approved

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Last modified December 11 02:45 EST 2023. Contains 367717 sequences. (Running on oeis4.)