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A036744 Penholodigital squares: squares containing each of the digits 1..9 exactly once. 8
139854276, 152843769, 157326849, 215384976, 245893761, 254817369, 326597184, 361874529, 375468129, 382945761, 385297641, 412739856, 523814769, 529874361, 537219684, 549386721, 587432169, 589324176, 597362481, 615387249, 627953481, 653927184, 672935481, 697435281, 714653289, 735982641, 743816529, 842973156, 847159236, 923187456 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Improved Mathematica formula provided. Because the range involved is only from Ceiling[Sqrt[123456789]]=11112 and Floor[Sqrt[987654321]]=31427, it only requires analyzing 20,315 numbers, versus 362,880 permutations of nine digits (as in the current formula). - Harvey P. Dale, Apr 17 2002
Since the sum of the digits is 45, the squares are all divisible by 3, so the given Mathematica formula could be sped up by a factor of 3, checking only multiples of 3 rather than all squares. - Joshua Zucker, Nov 28 2005
Eight-digit analog gives 5 squares: 13527684, 34857216, 65318724, 73256481, 81432576. - Zak Seidov, Mar 01 2011
LINKS
FORMULA
a(n) = A071519(n)^2.
MAPLE
lim:=floor(sqrt(987654321)): for n from 11112 by 3 to lim do d:=[op(convert(n^2, base, 10))]: pandig:=true: for k from 1 to 9 do if(numboccur(k, d)<>1)then pandig:=false: break: fi: od: if(pandig)then printf("%d, ", n^2): fi: od: # Nathaniel Johnston, Jun 22 2011
MATHEMATICA
Select[Range[11112, 31427]^2, Union[Drop[DigitCount[ # ], -1]] == {1} &]
PROG
(PARI) A036744 = [n^2 | n <- A071519] \\ or less efficient & more explicit:
A036744 = [n^2 | n <- [1e5\9..1e5\3], vecsort(digits(n^2)) == [1..9]] \\ M. F. Hasler, Jun 28 2023
CROSSREFS
Sequence in context: A034642 A109093 A217002 * A257643 A262532 A075130
KEYWORD
nonn,base,fini,full
AUTHOR
EXTENSIONS
More terms from Harvey P. Dale, Sep 26 2001
Keyword base added by Reinhard Zumkeller, May 16 2010
STATUS
approved

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Last modified March 19 02:55 EDT 2024. Contains 370952 sequences. (Running on oeis4.)