A028556 - OEIS

%I #10 Aug 11 2024 14:41:29

%S 0,5,77,252,525,1221,2112,21312,56165,73437,276672,1265621,2114112,

%T 2509052,29311392,69555596,71588517,122434221,126000621,540888045,

%U 5401221045,21183638112,69069096096,71149694117,79158385197,2752360632572,7320655560237,12278611687221

%N Palindromes of form k*(k+4).

%H Michael S. Branicky, <a href="/A028556/b028556.txt">Table of n, a(n) for n = 1..49</a>

%H P. De Geest, <a href="https://www.worldofnumbers.com/consemor.htm">Palindromic Quasipronics of the form n(n+x)</a>

%F a(n) = A028555(n) * (A028555(n) + 4). - _Michael S. Branicky_, Jan 26 2022

%o (Python)

%o from itertools import count, islice

%o def ispal(n): s = str(n); return s == s[::-1]

%o def agen():

%o     for k in count(0):

%o         if ispal(k*(k+4)):

%o             yield k*(k+4)

%o print(list(islice(agen(), 32))) # _Michael S. Branicky_, Jan 26 2022

%Y Cf. A028347, A028555.

%K nonn,base

%O 1,2

%A _Patrick De Geest_

%E a(26) and beyond from _Michael S. Branicky_, Jan 26 2022