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 A307764 Numbers m whose distinct prime factors are exactly the same as the distinct prime factors of each of the numbers obtained by deleting any single digit in the decimal expansion of m. 0
 2500, 3600, 9600, 25000, 36000, 96000, 250000, 360000, 960000, 2500000, 3600000, 9600000, 25000000, 36000000, 96000000, 250000000, 360000000, 960000000, 2500000000, 3600000000, 9600000000, 25000000000, 36000000000, 96000000000, 250000000000, 360000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Conjecture: a(3n-2) = 25*10^(n+1), a(3n-1) = 36*10^(n+1) and a(3n) = 96*10^(n+1). LINKS Table of n, a(n) for n=1..26. EXAMPLE 3600 is in the sequence because 3600, 360, 600 and 300 contain all the same prime factors 2, 3 and 5. MAPLE with(numtheory):nn:=10^10: for n from 100 to nn do: it:=0:x:=convert(n, base, 10):n0:=nops(x):d:=factorset(n): W:=array(1..n0-1): for i from 1 to n0 do : k:=0: for j from n0 by -1 to 1 do: if j<>i then k:=k+1: W[k]:=x[j]: else fi: od: s:=sum(‘W[i]*10^(n0-i-1)’, ‘i’=1..n0-1):d1:=factorset(s): if d=d1 then it:=it+1: else fi: od: if it=n0 then printf(`%d, `, n): else fi: od: MATHEMATICA rad[0] = 0; rad[n_] := Times @@ (First@# & /@ FactorInteger[n]); Select[Range[ 10^6], {rad[#]} == Union[rad /@ (FromDigits/@Subsets[(d = IntegerDigits[#]), {Length[d] - 1}])] &] (* Amiram Eldar, Jul 26 2019 *) CROSSREFS Cf. A027748. Sequence in context: A248548 A252315 A131523 * A062120 A220025 A253377 Adjacent sequences: A307761 A307762 A307763 * A307765 A307766 A307767 KEYWORD nonn,base AUTHOR Michel Lagneau, Jul 24 2019 STATUS approved

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Last modified February 29 07:00 EST 2024. Contains 370414 sequences. (Running on oeis4.)