A028564 Numbers k such that k*(k+7) is a palindrome.
0, 1, 4, 19, 26, 219, 664, 902, 2109, 2972, 2982, 9002, 21009, 29696, 90002, 210009, 223114, 292967, 669024, 900002, 942997, 2100009, 2109664, 2219779, 8972876, 9000002, 21000009, 21037924, 21117304, 21152824, 21155344, 28867722, 29802897, 29857886, 90000002
Offset: 1
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..49
- Patrick De Geest, Palindromic Quasipronics of the form n(n+x)
- Erich Friedman, What's Special About This Number? (See entries 664, 902, 2109, 2982, 9002.)
Programs
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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+7)): yield k print(list(islice(agen(), 26))) # Michael S. Branicky, Jan 26 2022
Extensions
a(32) and beyond from Michael S. Branicky, Jan 26 2022