OFFSET
1,1
COMMENTS
The smallest square in this sequence is 63504 = 252*252 = 144*441.
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..11195 (terms < 10^9)
EXAMPLE
252 = 12*21.
MATHEMATICA
Take[Union[ Transpose[ Select[Table[{n, n* FromDigits[Reverse[IntegerDigits[n]]]}, {n, 1000}], Mod[ #[[1]], 10] != 0 && #[[1]] != FromDigits[Reverse[IntegerDigits[ #[[1]]]]] &]][[2]]], 100]
upto2ndigits@n_ := Union@(If[(i = IntegerReverse@#) > #, i*#, Nothing] & /@Range@(10^n - 1)); upto2ndigits@3 (* Hans Rudolf Widmer, Sep 06 2024 *)
PROG
(Python)
from sympy import divisors
def ok(n): return any(n==d*int(s[::-1]) for d in divisors(n)[1:-1] if (s:=str(d))!=s[::-1] and s[-1]!="0")
print([k for k in range(36000) if ok(k)]) # Michael S. Branicky, Sep 07 2024
(Python) # instantly generates 44185 terms with n = 5
def aupto2ndigits(n): return(sorted(set(i*int(s[::-1]) for i in range(12, 10**n) if i%10 != 0 and (s:=str(i)) != s[::-1])))
print(aupto2ndigits(2))
# Michael S. Branicky, Sep 08 2024 after Hans Rudolf Widmer
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Tanya Khovanova, May 30 2007
EXTENSIONS
Offset corrected by Stefano Spezia, Sep 07 2024
STATUS
approved