A123132 Describe prime factorization of n (primes in ascending order and with repetition) (method A - initial term is 2).
12, 13, 22, 15, 1213, 17, 32, 23, 1215, 111, 2213, 113, 1217, 1315, 42, 117, 1223, 119, 2215, 1317, 12111, 123, 3213, 25, 12113, 33, 2217, 129, 121315, 131, 52, 13111, 12117, 1517, 2223, 137, 12119, 13113, 3215, 141, 121317, 143, 22111, 2315, 12123
Offset: 2
Examples
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. .....
Links
- Paolo P. Lava, Table of n, a(n) for n = 2..10000
- A. Frank & P. Jacqueroux, International Contest, 2001.
Programs
-
Mathematica
a[n_] := FromDigits@ Flatten@ IntegerDigits[ Reverse /@ FactorInteger@ n]; a/@ Range[2,30] (* Giovanni Resta, Jun 16 2013 *)
-
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
Comments