A053964 Numbers k such that k^2 contains only digits {4,7,9}.

2, 3, 7, 88, 212, 893, 69242288, 8819171038, 865996535661545126193725357

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Patrick De Geest, Squares containing at most three distinct digits, Index entries for related sequences

Author?, Source(txt)

Zhao Hui Du, C++ source code

Formula

a(n) = sqrt(A053965(n)).

Prog

(Python)
from itertools import product
from sympy import integer_nthroot
A053964_list = []
for l in range(1, 21):
    for p in product(*['479']*l):
        a, b = integer_nthroot(int(''.join(p)), 2)
        if b:
            A053964_list.append(a) # Chai Wah Wu, Apr 01 2021

Crossrefs

Cf. A053965.

Sequence in context: A065002 A288800 A247025 * A308730 A062578 A062529

Adjacent sequences: A053961 A053962 A053963 * A053965 A053966 A053967

Keyword

nonn,base,more

Author

Patrick De Geest, Mar 15 2000

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 03 2005

a(9) from Zhao Hui Du, Feb 29 2024

Status

approved