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A097569
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Right-truncatable Harshad numbers (zeros not permitted).
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2
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1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 18, 21, 24, 27, 36, 42, 45, 48, 54, 63, 72, 81, 84, 126, 216, 243, 247, 364, 423, 481, 486, 846, 2478, 8463, 24786
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listen;
history;
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internal format)
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OFFSET
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1,2
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COMMENTS
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Harshad numbers in which repeatedly deleting the rightmost digit gives a Harshad number at every step until a single-digit Harshad number remains. Sequence is finite with 24786 being the last term.
24786 can be proved to be the last term by a genetic approach (constructing the whole tree). - Carlos Rivera, Sep 19 2004
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LINKS
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Table of n, a(n) for n=1..35.
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MATHEMATICA
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harQ[n_]:=Module[{idn=IntegerDigits[n]}, !MemberQ[idn, 0]&&Divisible[n, Total[ idn]]]; rtQ[n_]:=Module[{idn=IntegerDigits[n], c}, c=Table[ FromDigits[ Take[ idn, i]], {i, Length[idn]}]; And@@(harQ/@c)]; Select[ Range[25000], rtQ] (* Harvey P. Dale, Oct 07 2013 *)
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CROSSREFS
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Cf. A005349.
Sequence in context: A334416 A217973 A097518 * A308561 A095160 A356350
Adjacent sequences: A097566 A097567 A097568 * A097570 A097571 A097572
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KEYWORD
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base,nonn,fini,full
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AUTHOR
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Jason Earls, Aug 28 2004
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STATUS
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approved
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