OFFSET

1,1

COMMENTS

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).

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..30

EXAMPLE

For example: 735 = 3*5*7^2 and 3792 = 2^4*3*79.

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

KEYWORD

base,nonn

AUTHOR

Tanya Khovanova, Aug 28 2006

EXTENSIONS

a(14) from Emmanuel Vantieghem, Nov 30 2016

Missing term 5581625072=5581||62507||2 inserted by Deron Stewart, Feb 15 2019

a(16)-a(22) from Giovanni Resta, Mar 04 2019

STATUS

approved