A028554 Palindromes of form n(n+3).

0, 4, 88, 868, 4554, 8008, 45154, 89698, 452254, 4526254, 8996998, 830333038, 862626268, 899969998, 4058008504, 45032023054, 45229592254, 89999699998, 405485584504, 4503764673054, 8187727277818, 8999996999998, 89178266287198, 455467838764554, 833066101660338

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

Also: Palindromes that are the sum of consecutive initial even composites. Sequence 4 + 6 + 8 + 10 + 12 + 14 + ... + z = n. For values of z see A058851. (Comment added by author 12/2000).

9*10^(2n)-3*10^n-2 for n >= 0 are terms. For n > 1, the first (and last digit) of a(n) is either 4 or 8. - Chai Wah Wu, Feb 20 2021

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..40
• P. De Geest, Palindromic Quasipronics
• P. De Geest, Palindromic Sums 2

Crossrefs

Cf. A028553, A058851.

Programs

Python

n, m, A028554_list = 4, 0, []
while n < 10**12:
    s = str(m)
    if s == s[::-1]:
        A028554_list.append(m)
    m += n
    n += 2 # Chai Wah Wu, Feb 20 2021

Extensions

More terms from Chai Wah Wu, Feb 20 2021