OFFSET
2,1
COMMENTS
Method A = 'frequency' followed by 'digit'-indication. Say 'what you see' in prime factors of n, n>1.
LINKS
Paolo P. Lava, Table of n, a(n) for n = 2..10000
A. Frank & P. Jacqueroux, International Contest, 2001.
EXAMPLE
2 has "one 2" in its prime decomposition, so a(2)=12.
3 has "one 3" in its prime decomposition, so a(3)=13.
4=2*2 has "two 2" in its prime decomposition, so a(4)=22.
5 has "one 5" in its prime decomposition, so a(5)=15.
6=2*3 has "one 2 and one 3" in its prime decomposition, so a(6)=1213.
.....
MATHEMATICA
a[n_] := FromDigits@ Flatten@ IntegerDigits[ Reverse /@ FactorInteger@ n]; a/@ Range[2, 30] (* Giovanni Resta, Jun 16 2013 *)
PROG
(PARI) for(n=2, 25, factn=factor(n); for(i=1, omega(n), print1(factn[i, 2], factn[i, 1])); print1(", "))
(PARI) a(n) = my(factn=factor(n), sout = ""); for(i=1, omega(n), sout = concat(sout, Str(factn[i, 2])); sout = concat(sout, Str(factn[i, 1]))); eval(sout); \\ Michel Marcus, Jun 29 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 30 2006
STATUS
approved