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 A080670 Literal reading of the prime factorization of n. 26
 1, 2, 3, 22, 5, 23, 7, 23, 32, 25, 11, 223, 13, 27, 35, 24, 17, 232, 19, 225, 37, 211, 23, 233, 52, 213, 33, 227, 29, 235, 31, 25, 311, 217, 57, 2232, 37, 219, 313, 235, 41, 237, 43, 2211, 325, 223, 47, 243, 72, 252, 317, 2213, 53, 233, 511, 237, 319, 229, 59, 2235 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Exponents equal to 1 are omitted and therefore this sequence differs from A067599. Here the first duplicate (ambiguous) term appears already with a(8)=23=a(6), in A067599 this happens only much later. - M. F. Hasler, Oct 18 2014 The number n = 13532385396179 = 13·53^2·3853·96179 = a(n) is (maybe the first?) nontrivial fixed point of this sequence, making it the first known index of a -1 in A195264. - M. F. Hasler, Jun 06 2017 LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 Tony Padilla and Brady Haran, 13532385396179, Numberphile Video, 2017 N. J. A. Sloane, Confessions of a Sequence Addict (AofA2017), slides of invited talk given at AofA 2017, Jun 19 2017, Princeton. Mentions this sequence. N. J. A. Sloane, Three (No, 8) Lovely Problems from the OEIS, Experimental Mathematics Seminar, Rutgers University, Oct 05 2017, Part I, Part 2, Slides. (Mentions this sequence) EXAMPLE 8=2^3, which reads 23, hence a(8)=23; 12=2^2*3, which reads 223, hence a(12)=223. MAPLE ifsSorted := proc(n)         local fs, L, p ;         fs := sort(convert(numtheory[factorset](n), list)) ;         L := [] ;         for p in fs do                 L := [op(L), [p, padic[ordp](n, p)]] ;         end do;         L ; end proc: A080670 := proc(n)         local a, p ;         if n = 1 then                 return 1;         end if;         a := 0 ;         for p in ifsSorted(n) do                 a := digcat2(a, op(1, p)) ;                 if op(2, p) > 1 then                         a := digcat2(a, op(2, p)) ;                 end if;         end do:         a ; end proc: # R. J. Mathar, Oct 02 2011 MATHEMATICA f[n_] := FromDigits[ Flatten@ IntegerDigits[ Flatten[ FactorInteger@ n /. {1 -> {}}]]]; f[1] = 1; Array[ f, 60] (* Robert G. Wilson v, Mar 02 2003 and modified Jul 22 2014 *) PROG (PARI) A080670(n)=if(n>1, my(f=factor(n), s=""); for(i=1, #f~, s=Str(s, f[i, 1], if(f[i, 2]>1, f[i, 2], ""))); eval(s), 1) \\ Charles R Greathouse IV, Oct 27 2013; case n=1 added by M. F. Hasler, Oct 18 2014 (PARI) A080670(n)=if(n>1, eval(concat(apply(f->Str(f[1], if(f[2]>1, f[2], "")), Vec(factor(n)~)))), 1) \\ M. F. Hasler, Oct 18 2014 (Haskell) import Data.Function (on) a080670 1 = 1 a080670 n = read \$ foldl1 (++) \$ zipWith (c `on` show) (a027748_row n) (a124010_row n) :: Integer where c ps es = if es == "1" then ps else ps ++ es -- Reinhard Zumkeller, Oct 27 2013 (Python) import sympy [int(''.join([str(y) for x in sorted(sympy.ntheory.factorint(n).items()) for y in x if y != 1])) for n in range(2, 100)] # compute a(n) for n > 1 # Chai Wah Wu, Jul 15 2014 CROSSREFS Cf. A037276, A067599, A230305, A230625, A027748, A124010, A288818. See A195330, A195331 for those n for which a(n) is a contraction. See also home primes, A037271. See A195264 for what happens when k -> a(k) is repeatedly applied to n. Partial sums: A287881, A287882. Sequence in context: A296254 A114749 A141458 * A288532 A073647 A073646 Adjacent sequences:  A080667 A080668 A080669 * A080671 A080672 A080673 KEYWORD nonn,base,look AUTHOR Jon Perry, Mar 02 2003 EXTENSIONS Edited and extended by Robert G. Wilson v, Mar 02 2003 STATUS approved

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Last modified August 21 04:22 EDT 2018. Contains 313932 sequences. (Running on oeis4.)