OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
FORMULA
EXAMPLE
First semiprime is 4; 4 is 2*2 -> 22.
Second semiprime is 6; 6 is 3*2 -> 32 (and not 23).
...
Eighth semiprime is 22; 22 is 2*11 -> 211 (and not 112).
PROG
(PARI) \\ here cd(x, y) returns base 10 concatenation.
cd(v1, v2)={10^(logint(v2, 10) + 1)*v1 + v2}
seq(n)={my(v=vector(n), k=0); for(i=1, #v, k++; while(2<>bigomega(k), k++); my(f=factor(k)[, 1]); v[i] = if(#f==1, cd(f[1], f[1]), max(cd(f[1], f[2]), cd(f[2], f[1])))); v} \\ Andrew Howroyd, Jan 08 2020
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Eric Angelini, May 09 2005
EXTENSIONS
Edited by N. J. A. Sloane, Apr 14 2008
Terms a(22) and beyond from Andrew Howroyd, Jan 08 2020
STATUS
approved