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

1,3

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.)

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+7)):
            yield k
print(list(islice(agen(), 26))) # Michael S. Branicky, Jan 26 2022

Crossrefs

Cf. A028563, A028565.

Sequence in context: A296602 A022135 A192193 * A282506 A047715 A003338

Adjacent sequences: A028561 A028562 A028563 * A028565 A028566 A028567

Keyword

nonn,base

Author

Patrick De Geest

Extensions

a(32) and beyond from Michael S. Branicky, Jan 26 2022

Status

approved