A028565 Palindromes of form k*(k+7).

0, 8, 44, 494, 858, 49494, 445544, 819918, 4462644, 8853588, 8913198, 81099018, 441525144, 882060288, 8100990018, 44105250144, 49781418794, 85831713858, 447597795744, 810009900018, 889249942988, 4410052500144, 4450696960544, 4927434347294, 80512566521508, 81000099000018

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..49
• Patrick De Geest, Palindromic Quasipronics of the form n(n+x)

Crossrefs

Cf. A028563, A028564.

Programs

Mathematica

Select[Table[k(k+7),{k,0,9000100}],PalindromeQ] (* Harvey P. Dale, Dec 17 2024 *)

Python

from itertools import count, islice
def ispal(n): s = str(n); return s == s[::-1]
def agen():
    for k in count(0):
        if ispal(k*(k+7)):
            yield k*(k+7)
print(list(islice(agen(), 28))) # Michael S. Branicky, Jan 26 2022

Formula

a(n) = A028564(n) * (A028564(n) + 7). - Michael S. Branicky, Jan 26 2022

Extensions

a(23) and beyond from Michael S. Branicky, Jan 26 2022