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A028553
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Numbers n such that n(n+3) is a palindrome.
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3
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0, 1, 8, 28, 66, 88, 211, 298, 671, 2126, 2998, 28814, 29369, 29998, 63701, 212206, 212671, 299998, 636776, 2122206, 2861419, 2999998, 9443423, 21341691, 28862883, 29999998, 212325206, 289053683, 294127328, 294174669, 299999998, 2134473706, 2946920844, 2999999998
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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Also: sum of the first n even composites is palindromic. Sequence is 4 + 6 + 8 + 10 + 12 + 14 + ... + z. For values of z see A058851. (Comment added by author 12/2000).
3*10^n-2 for n >= 0 are terms. For n>1, a(n) mod 10 is one of {1,3,4,6,8,9}. - Chai Wah Wu, Feb 20 2021
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LINKS
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Chai Wah Wu, Table of n, a(n) for n = 1..40
P. De Geest, Palindromic Quasipronics
P. De Geest, Palindromic Sums 2
Erich Friedman, What's Special About This Number? (See entries 298, 2126, 2998.)
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PROG
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(Python)
n, m, A028553_list = 0, 0, []
while n < 10**12:
s = str(m)
if s == s[::-1]:
A028553_list.append(n)
m += 2*(n+2)
n += 1 # Chai Wah Wu, Feb 20 2021
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CROSSREFS
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Cf. A058852, A028554.
Sequence in context: A007259 A134747 A083013 * A100182 A321237 A328535
Adjacent sequences: A028550 A028551 A028552 * A028554 A028555 A028556
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KEYWORD
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nonn,base,changed
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AUTHOR
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Patrick De Geest
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EXTENSIONS
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More terms from Chai Wah Wu, Feb 20 2021
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STATUS
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approved
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