OFFSET
1,2
COMMENTS
Invented by the HR concept formation program.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..11329
S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.
EXAMPLE
10 = 5 * tau(5).
PROG
(PARI) isok(n) = {for (k=1, n, if (k*numdiv(k) == n, return (1)); ); return (0); } \\ Michel Marcus, Dec 09 2014
(PARI)
up_to = 65536;
A036438list(up_to) = { my(v=vector(up_to), m = Map()); for(n=1, #v, mapput(m, n*numdiv(n), n)); my(k=0, u=0); while((k<#v)&&(u<#v), u++; if(mapisdefined(m, u), k++; v[k] = u)); vector(k, i, v[i]); };
v036438 = A036438list(up_to);
A036438(n) = v036438[n]; \\ Antti Karttunen, Jul 18 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Simon Colton (simonco(AT)cs.york.ac.uk)
STATUS
approved