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A121342
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Composite numbers that are a concatenation of their distinct prime divisors in some order.
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6
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735, 3792, 1341275, 13115375, 22940075, 29373375, 71624133, 311997175, 319953792, 1019127375, 1147983375, 1734009275, 5581625072, 7350032375, 17370159615, 33061224492, 103375535837, 171167303912, 319383665913, 533671737975, 2118067737975, 3111368374257
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OFFSET
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1,1
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COMMENTS
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Larger terms of this sequence were calculated by Giovanni Resta and Farideh Firoozbakht. This sequence is a subsequence of A083360 (Subsequence of sequence A083359 in which factors do not overlap in the number), which is a subsequence of A083359 (Visible Factor Numbers, or VPNs: numbers n with the property that every prime factor of n can be found in the decimal expansion of n and every digit of n can be found in a prime factor. No additional 0's and 1's are allowed). Also, this sequence is a subsequence of A096595 (Numbers n with the property that n is an anagram of the digits of the distinct prime factors of n).
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LINKS
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EXAMPLE
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For example: 735 = 3*5*7^2 and 3792 = 2^4*3*79.
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MATHEMATICA
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fQ[n_] := !PrimeQ@n && MemberQ[ FromDigits /@ (Flatten@# & /@ IntegerDigits[ Permutations[ First /@ FactorInteger@n]]), n]; Do[ If[fQ@n, Print@n], {n, 10^7/4}] (* Robert G. Wilson v, Sep 02 2006 *)
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PROG
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(PARI) isok(n) = {if (isprime(n), return (0)); my(vp = factor(n)[, 1], nb = #vp); for (i=0, nb!-1, my(vperm = numtoperm(nb, i), s = ""); for (i=1, #vperm, s = concat(s, vp[vperm[i]]); ); if (eval(s) == n, return (1)); ); return (0); } \\ Michel Marcus, Feb 19 2019
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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Missing term 5581625072=5581||62507||2 inserted by Deron Stewart, Feb 15 2019
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STATUS
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approved
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