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A028556
Palindromes of form k*(k+4).
2
0, 5, 77, 252, 525, 1221, 2112, 21312, 56165, 73437, 276672, 1265621, 2114112, 2509052, 29311392, 69555596, 71588517, 122434221, 126000621, 540888045, 5401221045, 21183638112, 69069096096, 71149694117, 79158385197, 2752360632572, 7320655560237, 12278611687221
OFFSET
1,2
FORMULA
a(n) = A028555(n) * (A028555(n) + 4). - Michael S. Branicky, Jan 26 2022
PROG
(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+4)):
yield k*(k+4)
print(list(islice(agen(), 32))) # Michael S. Branicky, Jan 26 2022
CROSSREFS
Sequence in context: A222533 A059856 A001513 * A364713 A214867 A330999
KEYWORD
nonn,base
EXTENSIONS
a(26) and beyond from Michael S. Branicky, Jan 26 2022
STATUS
approved