OFFSET
1,1
COMMENTS
If n = p_1^e_1 * ... * p_r^e_r with p_1 < ... < p_r, then the decimal encoding is p_1 e_1...p_r e_r. For example, 15 = 3^1 * 5^1, so has decimal encoding 3151.
a(12) > 10^10. [From Donovan Johnson, Mar 26 2010]
a(15) > 10^12. - Giovanni Resta, Aug 17 2016
EXAMPLE
The prime factorization of 21 = 3^1 * 7^1 with corresponding encoding 3171. 3171 = 21 * 151, a multiple of 21. So 21 is a term of the sequence.
MATHEMATICA
Select[Range[100000], Mod[FromDigits[Flatten[IntegerDigits /@ Flatten[FactorInteger[ # ]]]], # ] ==0 &]
PROG
(PARI) {a067598(a, b) = local(n, v); for(n=max(2, a), b, v=factor(n); if(eval(concat(vector(matsize(v)[1], k, concat(vector(matsize(v)[2], j, Str(v[k, j]))))))%n==0, print1(n, ", ")))}
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Joseph L. Pe, Jan 31 2002
EXTENSIONS
Edited and extended by Robert G. Wilson v, Feb 02 2002
Two more terms from Klaus Brockhaus, Feb 20 2002
a(10)-a(11) from Donovan Johnson, Mar 26 2010
a(12)-a(14) from Giovanni Resta, Aug 17 2016
STATUS
approved