A034307 Numbers n such that there are no oblong (promic) palindromes of length n.
2, 5, 9, 12, 18, 20, 30, 34
Offset: 1
Links
- P. De Geest, Palindromic pronic numbers of the form n(n+1)
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
272 belongs to the sequence as 272 = 16*17 is a palindrome.
Select[2*Accumulate[Range[15820000]],IntegerDigits[#] == Reverse[ IntegerDigits[#]]&] (* Harvey P. Dale, Sep 03 2013 *)
A028337_list, n = [], 0 for i in range(2,10**6,2): n += i s = str(n) if s == s[::-1]: A028337_list.append(n) # Chai Wah Wu, Jan 15 2015
palQ[n_] := Block[{d = IntegerDigits[n]}, d == Reverse[d]]; f[n_] := n^2 + n + 1; Select[Range[0, 10^5], palQ@ f@ # &] (* Giovanni Resta, Aug 29 2018 *)
Select[Range[0, 9999], PalindromeQ[#^2 + 4#] &] (* Alonso del Arte, Nov 10 2019 *)
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
print(list(islice(agen(), 32))) # Michael S. Branicky, Jan 25 2022
def palQ(n: Int, b: Int = 10): Boolean = n - Integer.parseInt(n.toString.reverse) == 0 (0 to 9999).filter((n: Int) => palQ(n * n + 4 * n)) // Alonso del Arte, Nov 10 2019