A028562 Palindromes of form k*(k+6).

0, 7, 55, 616, 19591, 76167, 515515, 749947, 7474747, 72999927, 236799997632, 769437734967, 1900289820091, 2998954598992, 5170703070715, 5934592954395, 29175111157192, 51175166157115, 57154688645175, 211106050601112, 570608929806075, 574823545328475

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..35
• P. De Geest, Palindromic Quasipronics of the form n(n+x)

Crossrefs

Cf. A028560, A028561.

Programs

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+6)):
            yield k*(k+6)
print(list(islice(agen(), 19))) # Michael S. Branicky, Jan 25 2022

Formula

a(n) = A028561(n) * (A028561(n) + 6). - Michael S. Branicky, Jan 25 2022

Extensions

a(20) and beyond from Michael S. Branicky, Jan 25 2022