OFFSET
1,1
COMMENTS
Numbers that are odd squares, 5 is their smallest prime factor, and are refactorable.
See A033950 for references. For any prime p, p^(p-1) is the smallest element of RF(p), the refactorable numbers whose smallest prime factor is p. Thus 5^(5-1) = 625 is the first element. Other elements would also be 5^4*17^4 or 5^16*17^4.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MAPLE
with(numtheory); RF5:=[]: p:=5: for w to 1 do for j from 1 to 12^5 do k:=2*j+1; if k mod 3 <> 0 and k mod p = 0 then n:=k^2; t:=tau(n); if (n mod t = 0) then RF5:=[op(RF5), n]; print(ifactor(n)); fi fi; od od;
PROG
(PARI) lista(kmax) = {my(m); for(k = 1, kmax, m = 25*(k\2*6-(-1)^k)^2; if(!(m % numdiv(m)), print1(m, ", "))); } \\ Amiram Eldar, Aug 01 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Walter Kehowski, Jun 20 2006
EXTENSIONS
a(37)-a(40) from Amiram Eldar, Aug 01 2024
STATUS
approved